Microchip dsPIC33FJ64MC510A Manual

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Analog-to-Digital

Converter (ADC)

Section 16. Analog-to-Digital Converter (ADC)

HIGHLIGHTS

This section of the manual contains the following major topics:

16.1 Introduction .................................................................................................................. 16-2

16.2 Control Registers ......................................................................................................... 16-6

16.3 Overview of Sample and Conversion Sequence ....................................................... 16-17

16.4 ADC Configuration..................................................................................................... 16-27

16.5 ADC Interrupt Generation .......................................................................................... 16-33

16.6 Analog Input Selection for Conversion....................................................................... 16-35

16.7 Specifying Conversion Results Buffering for Devices with DMA................................ 16-44

16.8 ADC Configuration Example ...................................................................................... 16-48

16.9 ADC Configuration for 1.1 Msps ................................................................................16-49

16.10 Sample and Conversion Sequence Examples for Devices without DMA .................. 16-51

16.11 Sample and Conversion Sequence Examples for Devices with DMA ....................... 16-63

16.12 Analog-to-Digital Sampling Requirements ................................................................. 16-73

16.13 Reading the ADC Result Buffer .................................................................................16-74

16.14 Transfer Functions ..................................................................................................... 16-76

16.15 ADC Accuracy/Error................................................................................................... 16-78

16.16 Connection Considerations........................................................................................ 16-78

16.17 Operation During Sleep and Idle Modes .................................................................... 16-79

16.18 Effects of a Reset....................................................................................................... 16-79

16.19 Special Function Registers ........................................................................................ 16-80

16.20 Design Tips ................................................................................................................ 16-81

16.21 Related Application Notes.......................................................................................... 16-82

16.22 Revision History ......................................................................................................... 16-83

dsPIC33F/PIC24H Family Reference Manual

16.1 INTRODUCTION

This document describes the features and associated operational modes of the Successive

Approximation (SAR) Analog-to-Digital Converter (ADC) available on the dsPIC33F/PIC24H

families of devices.

The ADC module can be configured by the user application to function as a 10-bit, 4-channel

ADC (for devices with 10-bit only ADC) or a 12-bit, single-channel ADC (for devices with

selectable 10-bit or 12-bit ADC).

Figure 16-1 illustrates a block diagram of the ADC module for devices with DMA. Figure 16-2

illustrates a block diagram of the ADC module for devices without DMA.

The dsPIC33F/PIC24H ADC module has the following key features:

• SAR conversion

• Up to 1.1 Msps conversion speed

• Up to 32 analog input pins

• External voltage reference input pins

• Four unipolar differential Sample and Hold (S&H) amplifiers

• Simultaneous sampling of up to four analog input pins

• Automatic Channel Scan mode

• Selectable conversion trigger source

• Up to 16-word conversion result buffer

• Selectable Buffer Fill modes (not available on all devices)

• DMA support, including Peripheral Indirect Addressing (not available on all devices)

• Operation during CPU Sleep and Idle modes

Depending on the device variant, the ADC module may have up to 32 analog input pins,

designated AN0-AN31. These analog inputs are connected by multiplexers to four S&H

amplifiers, designated CH0-CH3. The analog input multiplexers have two sets of control bits,

designated as MUXA (CHySA/CHyNA) and MUXB (CHySB/CHyNB). These control bits select a

particular analog input for conversion. The MUXA and MUXB control bits can alternatively select

the analog input for conversion. Unipolar differential conversions are possible on all channels

using certain input pins (see Figure 16-1 Figure 16-2 and ).

Channel Scan mode can be enabled for the CH0 S&H amplifier. Any subset of the analog inputs

(AN0 to AN31 based on availability) can be selected by the user application. The selected inputs

are converted in ascending order using CH0.

The ADC module supports simultaneous sampling using multiple S&H channels to sample the

inputs at the same time, and then performs the conversion for each channel sequentially. By

default, the multiple channels are sampled and converted sequentially.

For devices with DMA, the ADC module is connected to a single-word result buffer. However,

multiple conversion results can be stored in a DMA RAM buffer with no CPU overhead when

DMA is used with the ADC module. Each conversion result is converted to one of four 16-bit

output formats when it is read from the buffer.

Note: This family reference manual section is meant to serve as a complement to device

data sheets. Depending on the device variant, this manual section may not apply to

all dsPIC33F/PIC24H devices.

Please consult the note at the beginning of the “Analog-to-Digital Converter

(ADC)” chapter in the current device data sheet to check whether this document

supports the device you are using.

Device data sheets and family reference manual sections are available for

download from the Microchip Worldwide Web site at: http://www.microchip.com

dsPIC33F/PIC24H Family Reference Manual

Figure 16-1: ADC Block Diagram for Devices with DMA

SAR ADC

S/H0

S/H1

AN0

AN31

AN1

VREFL

CH0SB<4:0>

CH0NA CH0NB

AN0

AN3

CH123SA

AN9

VREFL

CH123SB

CH123NA CH123NB

AN6

S/H2

AN1

AN4

CH123SA

AN10

VREFL

CH123SB

CH123NA CH123NB

AN7

S/H3

AN2

AN5

CH123SA

AN11

VREFL

CH123SB

CH123NA CH123NB

AN8

CH1(2)

CH0

CH2(2)

CH3(2)

CH0SA<4:0>

CHANNEL

SCAN

CSCNA

Alternate

Note 1: VREF+, VREF- inputs can be multiplexed with other analog inputs. For details, refer to the “Pin Diagrams” section in the specific device

data sheet.

2: Channels 1, 2 and 3 are not applicable for the 12-bit mode of operation.

Input Selection

VREFH VREFL

V +REF (1) AV AVDD SS

V -REF (1)

VCFG<2:0>

Bus Interface

ADC1BUF0

dsPIC33F/PIC24H Family Reference Manual

16.2 CONTROL REGISTERS

The ADC module has ten Control and Status registers. These registers are:

•ADxCON1: ADCx Control Register 1

•ADxCON2: ADCx Control Register 2

•ADxCON3: ADCx Control Register 3

•ADxCON4: ADCx Control Register 4

•ADxCHS123: ADCx Input Channel 1, 2, 3 Select Register

•ADxCHS0: ADCx Input Channel 0 Select Register

•AD1CSSH: ADC1 Input Scan Select Register High

•ADxCSSL: ADCx Input Scan Select Register Low

•AD1PCFGH: ADC1 Port Configuration Register High

•ADxPCFGL: ADCx Port Configuration Register Low

The ADxCON1, ADxCON2 and ADxCON3 registers control the operation of the ADC module.

The ADxCON4 register sets up the number of conversion results stored in a DMA buffer for each

analog input in the Scatter/Gather mode for devices with DMA. The ADxCHS123 and ADxCHS0

registers select the input pins to be connected to the S&H amplifiers. The ADCSSH/L registers

select inputs to be sequentially scanned. The ADxPCFGH/L registers configure the analog input

pins as analog inputs or as digital I/O.

16.2.1 ADC Result Buffer

For devices with DMA, the ADC module contains a single-word result buffer, ADC1BUF0. For

devices without DMA, the ADC module contains a 16-word dual-port RAM, to buffer the results.

The 16 buffer locations are referred to as ADC1BUF0, ADC1BUF1, ADC1BUF2, ..., ADC1BUFE

and ADC1BUFF.

Note: After a device reset, the ADC buffer register(s) will contain unknown data.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

R/W-0 U-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0

ADON — ADSIDL ADDMABM(2) — AD12B(2) FORM<1:0>

bit 15 bit 8

R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0 R/W-0

HC,HS

R/C-0

HC, HS

SSRC<2:0> — SIMSAM ASAM SAMP DONE

bit 7 bit 0

Legend: HC = Cleared by hardware HS = Set by hardware C = Clear only bit

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15 ADON: ADC Operating Mode bit

1 = ADC module is operating

0 = ADC is off

bit 14 Unimplemented: Read as ‘0’

bit 13 ADSIDL: Stop in Idle Mode bit

1 = Discontinue module operation when device enters Idle mode

0 = Continue module operation in Idle mode

bit 12 ADDMABM: DMA Buffer Build Mode bit(3)

1 = DMA buffers are written in the order of conversion. The module provides an address to the DMA

channel that is the same as the address used for the non-DMA stand-alone buffer

0 = DMA buffers are written in Scatter/Gather mode. The module provides a Scatter/Gather address to

the DMA channel, based on the index of the analog input and the size of the DMA buffer

bit 11 Unimplemented: Read as ‘0’

bit 10 AD12B: 10-bit or 12-bit Operation Mode bit(2)

1 = 12-bit, 1-channel ADC operation

0 = 10-bit, 4-channel ADC operation

bit 9-8 FORM<1:0>: Data Output Format bits

For 10-bit operation:

11 sddd dddd dd00 0000 = Signed fractional (DOUT = , where s d = sign, = data)

10 = Fractional (DOUT = dddd dddd dd00 0000)

01 ssss sssd dddd dddd = Signed integer (DOUT = , where s d = sign, = data)

00 = Integer (DOUT = 0000 00dd dddd dddd)

For 12-bit operation:

11 sddd dddd dddd 0000 = Signed fractional (DOUT = , where s d = sign, = data)

10 = Fractional (DOUT = dddd dddd dddd 0000)

01 ssss sddd dddd dddd = Signed Integer (DOUT = , where s = sign, d = data)

00 = Integer (DOUT = 0000 dddd dddd dddd)

bit 7-5 SSRC<2:0>: Sample Clock Source Select bits

111 = Internal counter ends sampling and starts conversion (auto-convert)

110 = Reserved

101 = Motor Control PWM2 interval ends sampling and starts conversion(1)

100 = GP timer (Timer5 for ADC1, Timer3 for ADC2) compare ends sampling and starts conversion

(2)

011 = Motor Control PWM1 interval ends sampling and starts conversion(1)

010 = GP timer (Timer3 for ADC1, Timer5 for ADC2) compare ends sampling and starts conversion

001 = Active transition on INT0 pin ends sampling and starts conversion

000 = Clearing sample bit ends sampling and starts conversion

bit 4 Unimplemented: Read as ‘0’

Note 1: This clock source is not available on all devices. Refer to the specific device data sheet for availability.

2: This bit is not available on all devices. Refer to the “Analog-to-Digital Converter” chapter in the specific

device data sheet for availability.

dsPIC33F/PIC24H Family Reference Manual

bit 3 SIMSAM: Simultaneous Sample Select bit (only applicable when CHPS<1:0> = 01 1x or )

When AD12B = 1, SIMSAM is: U-0, Unimplemented, Read as ‘0’

1 = Samples CH0, CH1, CH2, CH3 simultaneously (when CHPS<1:0> = 1x); or

Samples CH0 and CH1 simultaneously (when CHPS<1:0> = 01)

0 = Samples multiple channels individually in sequence

bit 2 ASAM: ADC Sample Auto-Start bit

1 = Sampling begins immediately after last conversion. SAMP bit is auto-set

0 = Sampling begins when SAMP bit is set

bit 1 SAMP: ADC Sample Enable bit

1 = ADC S&H amplifiers are sampling

0 = ADC S&H amplifiers are holding

If ASAM = 0, software can write ‘1’ to begin sampling. Automatically set by hardware if ASAM = 1.

If SSRC = 000, software can write ‘0’ to end sampling and start conversion. If SSRC ≠ 000,

automatically cleared by hardware to end sampling and start conversion.

bit 0 DONE: ADC Conversion Status bit

1 = ADC conversion cycle is completed

0 = ADC conversion not started or in progress

Automatically set by hardware when analog-to-digital conversion is complete. Software can write ‘0’ to

clear DONE status (software not allowed to write ‘1’). Clearing this bit does NOT affect any operation

in progress. Automatically cleared by hardware at the start of a new conversion.

Note 1: This clock source is not available on all devices. Refer to the specific device data sheet for availability.

2: This bit is not available on all devices. Refer to the “Analog-to-Digital Converter” chapter in the specific

device data sheet for availability.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

R/W-0 R/W-0 R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0

VCFG<2:0> — — CSCNA CHPS<1:0>

bit 15 bit 8

R-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

BUFS — SMPI<3:0>(1,2) BUFM ALTS

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-13 VCFG<2:0>: Converter Voltage Reference Configuration bits

bit 12-11 Unimplemented: Read as ‘0’

bit 10 CSCNA: Input Scan Select bit

1 = Scan inputs for CH0+ during Sample A bit

0 = Do not scan inputs

bit 9-8 CHPS<1:0>: Channel Select bits

When AD12B = 1, CHPS<1:0> is: U-0, Unimplemented, Read as ‘0’

1x = Converts CH0, CH1, CH2 and CH3

01 = Converts CH0 and CH1

00 = Converts CH0

bit 7 BUFS: Buffer Fill Status bit (only valid when BUFM = 1)

1 = ADC is currently filling the second half of the buffer. The user application should access data in the

first half of the buffer

0 = ADC is currently filling the first half of the buffer. The user application should access data in the

second half of the buffer

bit 6 Unimplemented: Read as ‘0’

Note 1: For devices with DMA, the SMPI<3:0> bits are referred to as the Increment Rate for DMA Address Select

bits.

2: For devices without DMA, the SMPI<3:0> bits are referred to as the Number of Samples Per Interrupt

Select bits.

3: The VREF+ and VREF- pins are not available on all devices. Refer to the “Pin Diagrams” section in the

specific device data sheet for availability.

VREFH VREFL

000 AVDD AVss

001 External VREF+(3) AVss

010 AVDD External VREF-(3)

011 External VREF+(3) External VREF-(3)

1xx AVDD AVss

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ADRC — — SAMC<4:0>(1,2)

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ADCS<7:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15 ADRC: ADC Conversion Clock Source bit

1 = ADC Internal RC Clock

0 = Clock Derived from System Clock

bit 14-13 Unimplemented: Read as ‘0’

bit 12-8 SAMC<4:0>: Auto Sample Time bits(1,2)

11111 = 31 TAD

•

00001 = 1 T

00000 = 0 TAD

bit 7-0 ADCS<7:0>: ADC Conversion Clock Select bits

11111111 = Reserved

•

01000000 = Reserved

00111111 = TCY · (ADCS<7:0> + 1) = 64 · TCY = TAD

•

00000010 = TCY · (ADCS<7:0> + 1) = 3 · TCY = TAD

00000001 = TCY · (ADCS<7:0> + 1) = 2 · TCY = TAD

00000000 = TCY · (ADCS<7:0> + 1) = 1 · TCY = TAD

Note 1: This bit is only used when the SSRC<2:0> bits (ADxCON1<7:5>) = 111.

2: If SSRC<2:0> = 111, the SAMC bit should be set to at least ‘1’ when using one S&H channel or using

simultaneous sampling. When using multiple S&H channels with sequential sampling, the SAMC bit

should be set to ‘0’ for the fastest possible conversion rate.

dsPIC33F/PIC24H Family Reference Manual

U-0 U-0 U-0 U-0 U-0 U-0 U-0 U-0

— — — — — — — —

bit 15 bit 8

U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0

— — — — — DMABL<2:0>

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-3 Unimplemented: Read as ‘0’

bit 2-0 DMABL<2:0>: DMA Buffer Locations per Analog Input bits

111 = Allocates 128 words of buffer to each analog input

110 = Allocates 64 words of buffer to each analog input

101 = Allocates 32 words of buffer to each analog input

100 = Allocates 16 words of buffer to each analog input

011 = Allocates 8 words of buffer to each analog input

010 = Allocates 4 words of buffer to each analog input

001 = Allocates 2 words of buffer to each analog input

000 = Allocates 1 word of buffer to each analog input

Note: This register is not available in devices without DMA. Refer to the “Direct Memory Access (DMA)”

chapter in the specific device data sheet for availability.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0

— — — — — CH123NB<1:0> CH123SB

bit 15 bit 8

U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0

— — — — — CH123NA<1:0> CH123SA

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-11 Unimplemented: Read as ‘0’

bit 10-9 CH123NB<1:0>: Channel 1, 2, 3 Negative Input Select for Sample B bits

When AD12B = 1, CHxNB is: U-0, Unimplemented, Read as ‘0’

11 = CH1 negative input is AN9, CH2 negative input is AN10, CH3 negative input is AN11

10 = CH1 negative input is AN6, CH2 negative input is AN7, CH3 negative input is AN8

0x = CH1, CH2, CH3 negative input is V

REFL

bit 8 CH123SB: Channel 1, 2, 3 Positive Input Select for Sample B bit

When AD12B = 1, CHxSA is: U-0, Unimplemented, Read as ‘0’

1 = CH1 positive input is AN3, CH2 positive input is AN4, CH3 positive input is AN5

0 = CH1 positive input is AN0, CH2 positive input is AN1, CH3 positive input is AN2

bit 7-3 Unimplemented: Read as ‘0’

bit 2-1 CH123NA<1:0>: Channel 1, 2, 3 Negative Input Select for Sample A bits

When AD12B = 1, CHxNA is: U-0, Unimplemented, Read as ‘0’

11 = CH1 negative input is AN9, CH2 negative input is AN10, CH3 negative input is AN11

10 = CH1 negative input is AN6, CH2 negative input is AN7, CH3 negative input is AN8

0x = CH1, CH2, CH3 negative input is V

REFL

bit 0 CH123SA: Channel 1, 2, 3 Positive Input Select for Sample A bit

When AD12B = 1, CHxSA is: U-0, Unimplemented, Read as ‘0’

1 = CH1 positive input is AN3, CH2 positive input is AN4, CH3 positive input is AN5

0 = CH1 positive input is AN0, CH2 positive input is AN1, CH3 positive input is AN2

dsPIC33F/PIC24H Family Reference Manual

R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CH0NB — — CH0SB<4:0>(1)

bit 15 bit 8

R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CH0NA — — CH0SA<4:0>(1,2)

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15 CH0NB: Channel 0 Negative Input Select for Sample B bit

Same definition as bit 7.

bit 14-13 Unimplemented: Read as ‘0’

bit 12-8 CH0SB<4:0>: Channel 0 Positive Input Select for Sample B bits

(1)

Same definition as bit<4:0>.

bit 7 CH0NA: Channel 0 Negative Input Select for Sample A bit

1 = Channel 0 negative input is AN1

0 = Channel 0 negative input is V

REFL

bit 6-5 Unimplemented: Read as ‘0’

bit 4-0 CH0SA<4:0>: Channel 0 Positive Input Select for Sample A bits(1,2)

11111 = Channel 0 positive input is AN31

11110 = Channel 0 positive input is AN30

•

00010 = Channel 0 positive input is AN2

00001 = Channel 0 positive input is AN1

00000 = Channel 0 positive input is AN0

Note 1: The AN16 through AN31 pins are not available for ADC2.

2: These bits have no effect when the CSCNA bit (ADxCON2<10>) = 1.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CSS31 CSS30 CSS29 CSS28 CSS27 CSS26 CSS25 CSS24

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CSS23 CSS22 CSS21 CSS20 CSS19 CSS18 CSS17 CSS16

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-0 CSS<31:16>: ADC Input Scan Selection bits

(1,2)

1 = Select ANx for input scan

0 = Skip ANx for input scan

Note 1: ADC2 only supports analog inputs AN0-AN15; therefore, no ADC2 Input Scan Select Register High exists.

2: A maximum of 16 inputs (any) can be scanned.

Note: This register is not available in devices without DMA. Refer to the “Analog-to-Digital Converter (ADC)”

chapter in the specific device data sheet for availability.

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CSS15(3) CSS14(3) CSS13(3) CSS12 CSS11 CSS10 CSS9 CSS8

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CSS7 CSS6 CSS5 CSS4 CSS3 CSS2 CSS1 CSS0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-0 CSS<15:0>: ADC Input Scan Selection bits(1,2)

1 = Select ANx for input scan

0 = Skip ANx for input scan

Note 1: On devices with less than 16 analog inputs, all ADxCSSL bits can be selected by the user. However,

inputs selected for scan without a corresponding input on device convert VREF-.

2: A maximum of 16 inputs (any) can be scanned.

3: This bit is not available in devices without DMA. Refer to the “Analog-to-Digital Converter (ADC)”

chapter in the specific device data sheet for availability.

dsPIC33F/PIC24H Family Reference Manual

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PCFG31 PCFG30 PCFG29 PCFG28 PCFG27 PCFG26 PCFG25 PCFG24

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PCFG23 PCFG22 PCFG21 PCFG20 PCFG19 PCFG18 PCFG17 PCFG16

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-0 PCFG<31:16>: ADC Port Configuration Control bits(1,2)

1 = Port pin in Digital mode, port read input enabled, ADC input multiplexer connected to AVSS

0 = Port pin in Analog mode, port read input disabled, ADC samples pin voltage

Note 1: On devices with less than 32 analog inputs, all PCFG bits are R/W by user. However, PCFG bits are

ignored on ports without a corresponding input on device.

2: ADC2 only supports analog inputs AN0-AN15; therefore, no ADC2 Port Configuration register exists.

Note: This register is not available in devices without DMA. Refer to the “Analog-to-Digital Converter (ADC)”

chapter in the specific device data sheet for availability.

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PCFG15(3) PCFG14(3) PCFG13(3) PCFG12 PCFG11 PCFG10 PCFG9 PCFG8

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

PCFG7 PCFG6 PCFG5 PCFG4 PCFG3 PCFG2 PCFG1 PCFG0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15-0 PCFG<15:0>: ADC Port Configuration Control bits(1,2)

1 = Port pin in Digital mode, port read input enabled, ADC input multiplexer connected to AVSS

0 = Port pin in Analog mode, port read input disabled, ADC samples pin voltage

Note 1: On devices with less than 16 analog inputs, all PCFG bits are R/W by user. However, PCFG bits are

ignored on ports without a corresponding input on device.

2: On devices with two ADC modules, both AD1PCFGL and AD2PCFGL affect the configuration of port pins

multiplexed with AN0-AN15.

3: This bit is not available in devices without DMA. Refer to the “Analog-to-Digital Converter (ADC)”

chapter in the specific device data sheet for availability.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.3 OVERVIEW OF SAMPLE AND CONVERSION SEQUENCE

Figure 16-3 illustrates that the analog-to-digital conversion is a three step process:

1. The input voltage signal is connected to the sample capacitor.

2. The sample capacitor is disconnected from the input.

3. The stored voltage is converted to equivalent digital bits.

The two distinct phases, sample and conversion, are independently controlled.

Figure 16-3: Sample Conversion Sequence

16.3.1 Sample Time

Sample Time is when the selected analog input is connected to the sample capacitor. There is a

minimum sample time to ensure that the S&H amplifier provides a desired accuracy for the

analog-to-digital conversion (see 16.12 “Analog-to-Digital Sampling Requirements”).

The sampling phase can be set up to start automatically upon conversion or by manually setting

the Sample bit (SAMP) in the ADC Control Register 1 (ADxCON1<1>). The sampling phase is

controlled by the Auto-Sample bit (ASAM) in the ADC Control Register 1 (ADxCON1<2>).

Table 16-1 lists the options selected by the specific bit configuration.

Table 16-1: Start of Sampling Selection

If automatic sampling is enabled, the sampling time (TSMP) taken by the ADC module is equal to

the number of TAD cycles defined by the SAMC<4:0> bits (ADxCON3<12:8>), as shown by

Equation 16-1.

Equation 16-1: Sampling Time Calculation

If manual sampling is desired, the user software must provide sufficient time to ensure adequate

sampling time.

SAR

ADC

Sample Time Conversion Time

SOC

Trigger

Note: The ADC module requires a finite number of analog-to-digital clock cycles to start

conversion after receiving a conversion trigger or stopping the sampling process.

Refer to the TPCS parameter in the “Electrical Characteristics” chapter of the spe-

cific device data sheet for further details.

ASAM Start of Sampling Selection

0Manual sampling

1Automatic sampling

TSMP = SAMC<4:0> • TAD

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

Table 16-3: Sample Conversion Sequence Selection

16.3.3 Manual Sample and Manual Conversion Sequence

In the Manual Sample and Manual Conversion Sequence, setting the Sample bit (SAMP) in the

ADC Control Register 1 (ADxCON1<1>) initiates sampling, and clearing the SAMP bit terminates

sampling and starts conversion (see Figure 16-4). The user application must time the setting and

clearing of the SAMP bit to ensure adequate sampling time for the input signal. Example 16-1

illustrates a code sequence for Manual Sample and Manual Conversion.

Figure 16-4: Manual Sample and Manual Conversion Sequence

Example 16-1: Code Sequence for Manual Sample and Manual Conversion

ASAM SSRC<2:0> Description

0 000 Manual Sample and Manual Conversion Sequence

0 111 Manual Sample and Automatic Conversion Sequence

0 001

010

011

100

Manual Sample and Triggered Conversion Sequence

1 000 Automatic Sample and Manual Conversion Sequence

1 111 Automatic Sample and Automatic Conversion Sequence

1 001

010

011

100

Automatic Sample and Triggered Conversion Sequence

Sample Time Conversion Time

SAMP

Sample Time

3 4

Conversion

Note 1: Sampling is started by setting the SAMP bit in software.

2: Conversion is started by clearing the SAMP bit in software.

3: Conversion is complete.

4: Sampling is started by setting the SAMP bit in software.

5: Conversion is started by clearing the SAMP bit in software.

AD1CON1bits.SAMP = 1; // Start sampling

DelayUs(10); // Wait for sampling time (10us)

AD1CON1bits.SAMP = 0; // Start the conversion

while (!AD1CON1bits.DONE); // Wait for the conversion to complete

ADCValue = ADC1BUF0; // Read the conversion result

Note: Due to the internal delay within the ADC module, the SAMP bit will read as ‘0’ to the

user software after a small interval of time after the conversion has already begun.

In general, the time interval will be 2 TCY.

dsPIC33F/PIC24H Family Reference Manual

16.3.4 Automatic Sample and Manual Conversion Sequence

In the Automatic Sample and Manual Conversion Sequence, sampling starts automatically after

conversion of the previous sample. The user application must allocate sufficient time for

sampling before clearing the SAMP bit. Clearing the SAMP bit initiates conversion (see

Figure 16-5).

Figure 16-5: Automatic Sample and Manual Conversion Sequence

Example 16-2: Code Sequence for Automatic Sample and Manual Conversion

Sample Time Conversion Time

SAMP

Sample Time

3 4

Conversion

Note 1: Sampling is started automatically after conversion completion of the previous sample.

2: Conversion is started by clearing the SAMP bit in software.

3: Conversion is complete.

4: Sampling is started automatically after conversion completion of the previous sample.

5: Conversion is started by clearing the SAMP bit in software.

while (1) // Repeat continuously

{

DelayNmSec(100); // Sample for 100 ms

AD1CON1bits.SAMP = 0; // Start converting

while (!AD1CON1bits.DONE; // Conversion done?

AD1CON1bits.DONE = 0); // Clear conversion done status bit

ADCValue = ADC1BUF0; // If yes, then get the ADC value

} // Repeat

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.3.5 Automatic Sample and Automatic Conversion Sequence

16.3.5.1 CLOCKED CONVERSION TRIGGER

The Auto Conversion method provides a more automated process to sample and convert the

analog inputs as shown in Figure 16-6. The sampling period is self-timed and the conversion

starts automatically upon termination of a self-timed sampling period. The Auto Sample Time bits

(SAMC<4:0>) in the ADxCON3 register (ADxCON3<12:8>) select 0 to 31 ADC clock cycles (TAD)

for sampling period. Refer to the ecific device data“Electrical Characteristics” chapter of the sp

sheet for a minimum recommended sampling time (SAMC value).

The SSRC<2:0> bits are set to ‘ ’ to choose the internal counter as the sample clock source,111

which ends sampling and starts conversion.

Figure 16-6: Automatic Sample and Automatic Conversion Sequence

Sample Time Conversion Time

SAMP

Sample Time

3 4

Conversion

Note 1: Sampling starts automatically after conversion.

2: Conversion starts automatically upon termination of self timed sampling period.

3: Sampling starts automatically after conversion.

4: Conversion starts automatically upon termination of self timed sampling period.

N • TAD N • TAD

Conversion

dsPIC33F/PIC24H Family Reference Manual

16.3.5.2 EXTERNAL CONVERSION TRIGGER

In an Automatic Sample and Triggered Conversion Sequence, the sampling starts automatically

after conversion and the conversion is started upon trigger event from the selected peripheral,

as shown in Figure 16-7. This allows ADC conversion to be synchronized with the internal or

external events. The external conversion trigger is selected by configuring the SSRC<2:0> bits

to ‘001’, ‘010’ or ‘011’. See 16.4.7 “Conversion Trigger Sources” for various external

conversion trigger sources.

The ASAM bit should not be modified while the ADC module is turned on. If automatic sampling

is desired, the ASAM bit must be set before turning the module on. The ADC module does take

some amount of time to stabilize (see the TPDU parameter in the specific device data sheet);

therefore, if automatic sampling is enabled, there is not guarantee that the first ADC result will be

correct until the ADC module stabilizes. It may be necessary to discard the first ADC result

depending on the analog-to-digital clock speed.

Figure 16-7: Automatic Sample and Triggered Conversion Sequence

Sample Time Conversion Time

SAMP

Sample Time

3 4

Conversion

Note 1: Sampling starts automatically after conversion.

2: Conversion starts upon trigger event.

3: Sampling starts automatically after conversion.

4: Conversion starts upon trigger event.

Conversion

SOC Trigger

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.3.6 Multi-Channel Sample Conversion Sequence

Multi-channel ADC modules typically convert each input channel sequentially using an input

multiplexer. Simultaneously sampling multiple signals ensures that the snapshot of the analog

inputs occurs at precisely the same time for all inputs, as shown in Figure 16-8.

Certain applications require simultaneous sampling, especially when phase information exists

between different channels. Sequential sampling takes a snapshot of each analog input just

before conversion starts on that input, as shown in Figure 16-8. The sampling of multiple inputs

is not correlated. For example, motor control and power monitoring require voltage and current

measurements and the phase angle between them.

Figure 16-8: Simultaneous and Sequential Sampling

Figure 16-9 and Figure 16-10 illustrate the ADC module supports simultaneous sampling using

two S&H or four S&H channels to sample the inputs at the same instant and then perform the

conversion for each channel sequentially.

The Simultaneous Sampling mode is selected by setting Simultaneous Sampling bit (SIMSAM)

in the ADC Control Register 1 (ADxCON1<3>). By default, the channels are sampled and

converted sequentially. Table 16-4 lists the options selected by a specific bit configuration. The

CHPS<1:0> bits determine the channels to be sampled, either sequentially or simultaneously.

Table 16-4: Start of Sampling Selection

SIMSAM Sampling Mode

0Sequential sampling

1Simultaneous sampling

AN0

AN1

AN2

AN3

Simultaneous

Sampling

Sequential

Sampling

dsPIC33F/PIC24H Family Reference Manual

Figure 16-9: 2-Channel Simultaneous Sampling (ASAM = 1)

For simultaneous sampling, the total time taken to sample and convert the channels is shown by

Equation 16-4.

Equation 16-4: Channel Sample and Conversion Total Time, Simultaneous Sampling

Selected

Sample 1

CH0

CH1

Convert 1

SOC

Trigger

Sample 2

Convert 2

Sample/Convert Sequence 1 Sample/Convert Sequence 2

2 43

Note 1: CH0-CH1 Input multiplexer selects analog input for sampling. The selected analog input

is connected to the sample capacitor.

2: On SOC Trigger, CH0-CH1 sample capacitor is disconnected from the multiplexer to

simultaneously sample the analog inputs. The analog value captured in CH0 is

converted to equivalent digital bits.

3: The analog voltage captured in CH1 is converted to equivalent digital bits.

4: CH0-CH1 Input multiplexer selects next analog input for sampling. The selected analog

input is connected to the sample capacitor.

5: On SOC Trigger, CH0-CH1 sample capacitor is disconnected from the multiplexer to

simultaneously sample the analog inputs. The analog value captured in CH0 is

converted to equivalent digital bits.

TSIM TSIM

TS I M TS M P M TC ONV

⋅( )+=

Where:

TSIM = Total time to sample and convert multiple channels with simultaneous sampling.

TSMP = Sampling Time (see Equation 16-1)

TCONV = Conversion Time (see Equation 16-2)

M = Number of channels selected by the CHPS<1:0> bits.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

Figure 16-10: 4-Channel Simultaneous Sampling

Figure 16-11 and Figure 16-12 illustrate that by default, the multiple channels are sampled and

converted sequentially.

For sequential sampling, the total time taken to sample and convert the channels is shown in

Equation 16-5.

Equation 16-5: Channel Sample and Conversion Total Time, Sequential Sampling

Selected

Sample 1

CH0

CH1

Sample 1

CH2

CH3

Convert 1

SOC

Trigger

Convert 1

Sample 2

Convert 2

Convert2

Sample/Convert Sequence 1 Sample/Convert Sequence 2

1 2 4 73 5 6

Note 1: CH0-CH3 Input multiplexer selects analog input for sampling. The selected analog input is connected to the

sample capacitor.

2: On SOC Trigger, CH0-CH3 sample capacitor is disconnected from the multiplexer to simultaneously sample

the analog inputs. The analog value captured in CH0 is converted to equivalent digital bits.

3: The analog voltage captured in CH1 is converted to equivalent digital bits.

4: The analog voltage captured in CH2 is converted to equivalent digital bits.

5: The analog voltage captured in CH3 is converted to equivalent digital bits.

6: CH0-CH3 Input multiplexer selects next analog input for sampling. The selected analog input is connected to

the sample capacitor.

7: On SOC Trigger, CH0-CH3 sample capacitor is disconnected from the multiplexer to simultaneously sample

the analog inputs. The analog value captured in CH0 is converted to equivalent digital bits.

TSIM TSIM

TSEQ M TCONV

⋅=

Where:

TSEQ = Total time to sample and convert multiple channels with sequential sampling.

TCONV

= Conversion Time (see Equation 16-2)

TSMP

= Sampling Time (see Equation 16-1)

M = Number of channels selected by the CHPS<1:0> bits.

(if M > 1)

TSEQ TSMP TCONV

+= (if M = 1)

When TSMP < TCONV,

dsPIC33F/PIC24H Family Reference Manual

Figure 16-11: 2-Channel Sequential Sampling (ASAM = 1)

Figure 16-12: 4-Channel Sequential Sampling

Sample 1

CH0

CH1

Convert 1

SOC

Trigger

Sample 2

Convert 2

Sample/Convert Sequence 1 Sample/Convert Sequence 2

Sample 2 Sample 3

1 2 4

Note 1: CH0-CH1 Input multiplexer selects analog input for sampling. The selected analog input is connected to

the sample capacitor.

2: On SOC Trigger, CH0 sample capacitor is disconnected from the multiplexer to hold the input voltage

constant during conversion. The analog value captured in CH0 is converted to equivalent digital bits.

3: The CH0 multiplexer output is connected to sample capacitor after conversion. CH1 sample capacitor is

disconnected from the multiplexer to hold the input voltage constant during conversion. The analog value

captured in CH1 is converted to equivalent digital bits.

4: The CH1 multiplexer output is connected to sample capacitor after conversion. CH0-CH1 Input multiplexer

selects next analog input for sampling.

5: On SOC Trigger, CH0 sample capacitor is disconnected from the multiplexer to hold the input voltage

constant during conversion. The analog value captured in CH0 is converted to equivalent digital bits.

Sample 1

CH0

CH1

CH2

CH3

Convert 1

Convert 2

Convert 1

SOC

Trigger

Sample 1

Convert 2

Convert 3

Convert 2Sample 2

Sample 2

Sample/Convert Sequence 1 Sample/Convert Sequence 2

Sample 2

Sample 3

12473 56

Note 1: CH0-CH3 Input multiplexer selects analog input for sampling. The selected analog input is connected to the

sample capacitor.

2: On SOC Trigger, CH0 sample capacitor is disconnected from the multiplexer to hold the input voltage constant

during conversion. The analog value captured in valent digital bits. CH0 is converted to equi

3: The CH0 multiplexer output is connected to sample capacitor after conversion. CH1 sample capacitor is

disconnected from the multiplexer to hold the input voltage constant during conversion. The analog value

captured in CH1 is converted to equivalent digital bits.

4: The CH1 multiplexer output is connected to sample capacitor after conversion. CH2 sample capacitor is

disconnected from the multiplexer to hold the input voltage constant during conversion. The analog value

captured in CH2 is converted to equivalent digital bits.

5: The CH2 multiplexer output is connected to sample capacitor after conversion. CH3 sample capacitor is

disconnected from the multiplexer to hold the input voltage constant during conversion. The analog value

captured in CH3 is converted to equivalent digital bits.

6: The CH3 multiplexer output is connected to sample capacitor after conversion. CH0-CH3 Input multiplexer

selects next analog input for sampling.

7: On SOC Trigger, CH0 sample capacitor is disconnected from the multiplexer to hold the input voltage constant

during conversion. The analog value captured in CH0 is converted to equivalent digital bits.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.4 ADC CONFIGURATION

16.4.1 ADC Operational Mode Selection

The 12-bit Operation Mode bit (AD12B) in the ADC Control Register 1 (ADxCON1<10>) allows

the ADC module to function as either a 10-bit, 4-channel ADC (default configuration) or a 12-bit,

single-channel ADC. Table 16-5 lists the options selected by different bit settings.

Table 16-5: ADC Operational Mode

16.4.2 ADC Channel Selection

In 10-bit mode (AD12B = 0), the user application can select 1-channel (CH0), 2-channel (CH0,

CH1) or 4-channel mode (CH0-CH3) using the Channel Select bits (CHPS<1:0>) in the ADC

Control register (ADxCON2<9:8>). In 12-bit mode, the user application can only use CH0.

Table 16-6 lists the number of channels selected for the different bit settings.

Table 16-6: 10-bit ADC Channel Selection

16.4.3 Voltage Reference Selection

The voltage references for analog-to-digital conversions are selected using the Voltage

Reference Configuration bits (VCFG<2:0>) in the ADC Control register (ADxCON2<15:13>). The

voltage reference high (VREFH) and the voltage reference low (VREFL) to the ADC module can be

supplied from the internal AVDD and AVSS voltage rails or the external VREF+ and VREF- input

pins. The external voltage reference pins can be shared with the AN0 and AN1 inputs on low pin

count devices. The ADC module can still perform conversions on these pins when they are

shared with the VREF+ and VREF- input pins. The voltages applied to the external reference pins

must meet certain specifications. For details, refer to the “Electrical Characteristics” chapter

of the specific device data sheet. In addition, refer to the “Pin Diagrams” section in the specific

device data sheet for the availability of the VREF+ and VREF- pins.

Table 16-7: Voltage Reference Selection

Note 1: The ADC module must be disabled before the AD12B bit is modified.

2: 12-bit mode is not available on all devices. Refer to the “Analog-to-Digital

Converter (ADC)” chapter in the specific device data sheet for availability.

AD12B Channel Selection

010-bit, 4-channel ADC

112-bit, single-channel ADC

CHPS<1:0> Channel Selection

00 CH0

01 Dual Channel (CH0, CH1)

1x Multi-Channel (CH0-CH3)

VCFG<2:0> VREFH VREFL

000 AV AVDD SS

001 VREF+ AVSS

010 AVDD VREF-

011 VREF+ VREF-

1xx AVDD AVSS

dsPIC33F/PIC24H Family Reference Manual

16.4.4 ADC Clock Selection

The ADC module can be clocked from the instruction cycle clock (TCY) or by using the dedicated

internal RC clock (see Figure 16-13). When using the instruction cycle clock, a clock divider

drives the instruction cycle clock and allows a lower frequency to be chosen. The clock divider is

controlled by the ADC Conversion Clock Select bits (ADCS<7:0>) in the ADC Control register

(ADxCON3<7:0>), which allows 64 settings, from 1:1 to 1:64, to be chosen.

For correct analog-to-digital conversion, the ADC Clock period (TAD) must be a minimum of

75 ns.

Equation 16-6 shows the ADC Clock period (TAD) as a function of the ADCS control bits and the

device instruction cycle clock period, TCY.

Equation 16-6: ADC Clock Period

The ADC module has a dedicated internal RC clock source that can be used to perform

conversions. The internal RC clock source is used when analog-to-digital conversions are

performed while the device is in the Sleep mode. The internal RC oscillator is selected by setting

the ADC Conversion Clock Source bit (ADRC) in ster 3 (ADxCON3<15>). the ADC Control Regi

When the ADRC bit is set, the ADCS<7:0> bits have no effect on the ADC operation.

Figure 16-13: ADC Clock Generation

16.4.5 Output Data Format Selection

Figure 16-14 illustrates the ADC result is available in four different numerical formats. The Data

Output Format bits (FORM<1:0>) in the ADC Control register (ADxCON1<9:8>), selects the

output data format. Table 16-8 lists the ADC output format for different bit settings.

Note: Refer to the “Electrical Characteristics” chapter in the specific device data sheet

for ADRC frequency specifications.

If ADRC = 0

ADC Clock Period (TAD) = TCY • (ADCS + 1)

If ADRC = 1

ADC Clock Period (TAD) = TADRC

ADCS<7:0>

ADRC

ADC Clock (TAD)

TCY

ADC Internal RC

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

Table 16-8: Voltage Reference Selection

Figure 16-14: ADC Output Format

FORM<1:0> Data Information Selection

11 Signed Fractional Format

10 Unsigned Fractional format

01 Signed Integer format

00 Unsigned Integer format

0000 0000 0000 0000 (0)

0000 0011 1111 1111 (1023)

0000 0010 0000 0000

(512)

1111 1110 0000 0000 (-512)

0000 0001 1111 1111 (511)

0000 0000 0000 0000 (0)

0000 0011 1111 1111 (4095)

0000 0010 0000 0000 (2048)

1111 1000 0000 0010 (-2046)

0000 0111 1111 1101 (2045)

0000 0000 0000 0000 (0)

10-bit ADC 12-bit ADC

FORM = 0b00

Unsigned

Integer

FORM = 0b01

Signed

Integer

0000 0000 0000 0000 (0)

1111 1111 1100 0000 (+0.999)

1000 0000 0000 0000 (0.5)

1000 0000 0000 0000 (-1)

0111 1111 1100 0000 (+0.999)

0000 0000 0000 0000 (0)

VREFH

VREFL

0000 0000 0000 0000 (0)

FORM = 0b10

Unsigned

Fraction (Q16)

FORM = 0b11

Signed

Fraction (Q15)

Input

0111 1111 1111 0000 (+0.999)

1000 0000 0000 0000 (-1)

VREFH

VREFL

1000 0000 0000 0000 (0.5)

Input

0000 0000 0000 0000 (0)

1111 1111 1111 0000 (+0.999)

VREFH

VREFL Input

VREFH

VREFL Input

VREFH

VREFL Input

VREFH

VREFL Input

VREFH

VREFL Input

VREFH

VREFL Input

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.4.7.3 MOTOR CONTROL PWM SPECIAL EVENT TRIGGER

(dsPIC33F MOTOR CONTROL DEVICES ONLY)

The PWM module has an event trigger that allows analog-to-digital conversions to be

synchronized to the PWM time base. When SSRC<2:0> = 011, the analog-to-digital sampling

and conversion times occur at any user programmable point within the PWM period. The Special

Event Trigger allows the user to minimize the delay between the time when the analog-to-digital

conversion results are acquired and the time when the duty cycle value is updated.

The application should set the ASAM bit in order to ensure that the ADC module has sampled

the input sufficiently before the next conversion trigger arrives.

16.4.8 Configuring Analog Port Pins

The Analog/Digital Pin Configuration register (ADxPCFGL) specifies the input condition of device

pins used as analog inputs. Along with the Data Direction register (TRISx) in the Parallel I/O Port

module, these registers control the operation of the ADC pins.

A pin is configured as an analog input when the corresponding PCFGn bit (ADxPCFGL<n>) is

clear. The ADxPCFGL register is cleared at Reset, causing the ADC input pins to be configured

for analog input by default at Reset.

When configured for analog input, the associated port I/O digital input buffer is disabled so that

it does not consume current.

The port pins that are desired as analog inputs must have their corresponding TRIS bit set,

specifying the port input. If the I/O pin associated with an analog-to-digital input is configured as

an output, the TRIS bit is cleared and the digital output level (VOH or VOL) of the port is converted.

After a device Reset, all TRIS bits are set.

A pin is configured as a digital I/O when the corresponding PCFGn bit is set. In this configuration,

the input to the analog multiplexer is connected to AVSS.

16.4.9 Enabling the ADC Module

When the ADON bit (ADxCON1<15>) is ‘1’, the module is in active mode and is fully powered

and functional.

When ADON is ‘0’, the module is disabled. The digital and analog portions of the circuit are

turned off for maximum current savings.

To return to the active mode from the off mode, the user application must wait for the analog

stages to stabilize. For the stabilization time, refer to the “Electrical Characteristics” chapter

of the specific device data sheet.

Note 1: When the ADC Port register is read, any pin configured as an analog input reads

as a ‘0’.

2: Analog levels on any pin that is defined as a digital input may cause the input buffer

to consume current that is out of the device specification.

Note: The SSRC<2:0>, SIMSAM, ASAM, CHPS<1:0>, SMPI<3:0>, BUFM and ALTS bits,

as well as the ADCON3 and ADCSSL registers, should not be written to, while

ADON = 1. This would lead to indeterminate results.

dsPIC33F/PIC24H Family Reference Manual

16.4.10 Turning the ADC Module Off

Clearing the ADON bit disables the ADC module (stops any scanning, sampling and conversion

processes). In this state, the ADC module still consumes some current. Setting the ADxMD bit in

the PMD register will disable the ADC module and will stop the ADC clock source, which reduces

device current consumption. Note that setting the ADxMD bit and then clearing the bit will reset

the ADC module registers to their default state. Additionally, any digital pins that share their

function with an ADC input pin revert to the analog function. While the ADxMD bit is set, these

pins will be set to digital function. In this case, the ADxPCFG bits will not have any effect.

Note: Clearing the ADON bit during a conversion will abort the current analog-to-digital

conversion. The ADC buffer will not be updated with the partially completed

conversion sample.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.5 ADC INTERRUPT GENERATION

With DMA enabled, the SMPI<3:0> bits (ADxCON2<5:2>) determine the number of

sample/conversion operations per channel (CH0/CH1/CH2/CH3) for every DMA

address/increment pointer.

The SMPI<3:0> bits have no effect when the ADC module is set up such that DMA buffers are

written in Conversion Order mode.

If DMA transfers are enabled, the SMPI<3:0> bits must be cleared, except when channel

scanning or alternate sampling is used. For more details on SMPI<3:0> setup requirements, see

16.7 “Specifying Conversion Results Buffering for Devices with DMA”.

When the SIMSAM bit (ADxCON1<3>) specifies sequential sampling, regardless of the number

of channels specified by the CHPS<1:0> bits (ADxCON2<9:8>), the ADC module samples once

for each conversion and data sample in the buffer. The value specified by the DMAxCNT register

for the DMA channel being used corresponds to the number of data samples in the buffer.

For devices with DMA, interrupts are generated after every conversion, which sets the DONE bit

since it reflects the interrupt flag (ADxIF) setting.

For devices without DMA, as conversions are completed, the ADC module writes the results of

the conversions into the analog-to-digital result buffer. The ADC result buffer is an array of

sixteen words, accessed through the SFR space. The user application may attempt to read each

analog-to-digital conversion result as it is generated. However, this might consume too much

CPU time. Generally, to simplify the code, the module fills the buffer with results and generates

an interrupt when the buffer is filled. The ADC module supports 16 result buffers. Therefore, the

maximum number of conversions per interrupt must not exceed 16.

The number of conversion per ADC interrupt depends on the following parameters, which can

vary from one to 16 conversions per interrupt.

• Number of S&H channels selected

• Sequential or Simultaneous Sampling

• Samples Convert Sequences Per Interrupt bits (SMPI<3:0>) settings

Table 16-9 lists the number of conversions per ADC interrupt for different configuration modes.

Table 16-9: Samples Per Interrupt in Alternate Sampling Mode

The DONE bit (ADxCON1<0>) is set when an ADC interrupt is generated to indicate completion

of a required sample/conversion sequence. This bit is automatically cleared by the hardware at

the beginning of the next sample/conversion sequence.

On devices without DMA, interrupt generation is based on the SMPI<3:0> and CHPS bits, so the

DONE bit is not set after every conversion, but is set when the Interrupt Flag (ADxIF) is set.

CHPS<1:0> SIMSAM SMPI<3:0> Conversions/

Interrupt Description

00 x N-1 N 1-Channel mode

01 0 N-1 N 2-Channel Sequential Sampling mode

1x 0 N-1 N 4-Channel Sequential Sampling mode

01 1 N-1 2 • N 2-Channel Simultaneous Sampling mode

1x 1 N-1 4 • N 4-Channel Simultaneous Sampling mode

Note 1: In 2-channel Simultaneous Sampling mode, SMPI<3:0> bit settings must be less

than eight.

2: In 4-channel Simultaneous Sampling mode, SMPI<3:0> bit settings must be less

than four.

dsPIC33F/PIC24H Family Reference Manual

16.5.1 Buffer Fill Mode

When the Buffer Fill Mode bit (BUFM) in the ADC Control Register 2 (ADxCON2<1>) is ‘1’, the

16-word results buffer is split into two 8-word groups: a lower group (ADC1BUF0 through

ADC1BUF7) and an upper group (ADC1BUF8 through ADC1BUFF). The 8-word buffers

alternately receive the conversion results after each ADC interrupt event. When the BUFM bit is

set, each buffer size is equal to eight. Therefore, the maximum number of conversions per

interrupt must not exceed eight.

When the BUFM bit is ‘0’, the complete 16-word buffer is used for all conversion sequences. The

decision to use the split buffer feature depends on the time available to move the buffer contents,

after the interrupt, as determined by the application.

If the application can quickly unload a full buffer within the time taken to sample and convert one

channel, the BUFM bit can be ‘0’, and up to 16 conversions may be done per interrupt. The

application has one sample/convert time before the first buffer location is overwritten. If the

processor cannot unload the buffer within the sample and conversion time, the BUFM bit should

be ‘1’. For example, if an ADC interrupt is generated every eight conversions, the processor has

the entire time between interrupts to move the eight conversions out of the buffer.

16.5.2 Buffer Fill Status

When the conversion result buffer is split using the BUFM control bit, the BUFS Status bit

(ADxCON2<7>) indicates, half of the buffer that the ADC module is currently writing. If BUFS = 0,

the ADC module is filling the lower group, and the user application should read conversion values

from the upper group. If BUFS = 1, the situation is reversed, and the user application should read

conversion values from the lower group.

dsPIC33F/PIC24H Family Reference Manual

16.6.2 Alternate Input Selection Mode

In an Alternate Input Selection mode, the MUXA and MUXB control bits select the channel for

conversion. The ADC completes one sweep using the MUXA selection, and then another sweep

using the MUXB selection, and then another sweep using the MUXA selection, and so on. The

Alternate Input Selection mode is enabled by setting the Alternate Sample bit (ALTS) in the ADC

Control Register 2 (ADxCON2<0>).

The analog input multiplexer is controlled by the AD1CHS123 and AD1CHS0 registers. There

are two sets of control bits designated as MUXA (CHySA/CHyNA) and MUXB (CHySB/CHyNB)

to select a particular input source for conversion. The MUXB control bits are used in Alternate

Input Selection mode.

Table 16-11: Analog Input Selection

For Alternate Input Selection mode in devices without DMA, an ADC interrupt must be generated

after an even number of sample/conversion sequences by programming the Samples Convert

Sequences Per Interrupt bits (SMPI<3:0>). Table 16-12 lists the valid SMPI values for Alternate

Input Selection mode in different ADC configurations.

Table 16-12: Valid SMPI Values for Alternate Input Selection Mode

Example 16-4 shows the code sequence to set up the ADC module for Alternate Input Selection

mode for devices without DMA in the 4-Channel Simultaneous Sampling configuration.

Figure 16-15 illustrates the ADC module operation sequence.

MUXA MUXB

Control bits Analog Inputs Control bits Analog Inputs

CH0 +ve CH0SA<4:0> AN0 to AN31 CH0SB<4:0> AN0 to AN31

-ve CH0NA VREF-, AN1 CH0NB VREF-, AN1

CH1 +ve CH123SA AN0, AN3 CH123SB AN0, AN3

-ve CH123NA<1:0> AN6, AN9, VREF REF- CH123NB<1:0> AN6, AN9, V -

CH2 +ve CH123SA AN1, AN4 CH123SB AN1, AN4

-ve CH123NA<1:0> AN7, AN10, VREF- CH123NB<1:0> AN7, AN10, VREF-

CH3 +ve CH123SA AN2, AN5 CH123SB AN2, AN5

-ve CH123NA<1:0> AN8, AN11, VREF- CH123NB<1:0> AN8, AN11, VREF-

Note: Not all inputs are present on all devices.

CHPS<1:0> SIMSAM SMPI<3:0>

(Decimal)

Conversions/

Interrupt Description

00 x 1,3,5,7,9,11,13,15 2,4,6,8,10,12,14,16 1-Channel mode

01 0 3,7,11,15 4,8,12,16 2-Channel Sequential

Sampling mode

1x 0 7,15 8,16 4-Channel Sequential

Sampling mode

01 1 1,3,5,7 4,8,12,16 2-Channel Simultaneous

Sampling mode

1x 1 1,3 8,16 4-Channel Simultaneous

Sampling mode

Note: On ADC Interrupt, the ADC internal logic is initialized to restart the conversion

sequence from the beginning.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

Example 16-4: Code Sequence to Set Up ADC for Alternate Input Selection Mode for 4-Channel

Simultaneous Sampling (Devices without DMA)

Figure 16-15: Alternate Input Selection in 4-Channel Simultaneous Sampling Configuration (Devices without

DMA)

AD1CON1bits.AD12B = 0; // Select 10-bit mode

AD1CON2bits.CHPS = 3; // Select 4-channel mode

AD1CON1bits.SIMSAM = 1; // Enable Simultaneous Sampling

AD1CON2bits.ALTS = 1; // Enable Alternate Input Selection

AD1CON2bits.SMPI = 1; // Select 8 conversion between interrupt

AD1CON1bits.ASAM = 1; // Enable Automatic Sampling

AD1CON1bits.SSRC = 2; // Timer3 generates SOC trigger

// Initialize MUXA Input Selection

AD1CHS0bits.CH0SA = 6; // Select AN6 for CH0 +ve input

AD1CHS0bits.CH0NA = 0; // Select VREF- for CH0 -ve input

AD1CHS123bits.CH123SA = 0; // Select CH1 +ve = AN0, CH2 +ve = AN1, CH3 +ve = AN2

AD1CHS123bits.CH123NA = 0; // Select VREF- for CH1/CH2/CH3 -ve inputs

// Initialize MUXB Input Selection

AD1CHS0bits.CH0SB = 7; // Select AN7 for CH0 +ve input

AD1CHS0bits.CH0NB = 0; // Select VREF- for CH0 -ve input

AD1CHS123bits.CH123SB = 1; // Select CH1 +ve = AN3, CH2 +ve = AN4, CH3 +ve = AN5

AD1CHS123bits.CH124NB = 0; // Select VREF- for CH1/CH2/CH3 -ve inputs

Sample

(AN6)

Sample

(AN0)

CH0

CH1

Sample

(AN1)

Sample

(AN2)

CH2

CH3

Convert

(AN6)

Convert

(AN0)

Convert

(AN1)

SOC

Trigger

Convert

(AN2)

Sample

(AN7)

Sample

(AN3)

Sample

(AN4)

Sample

(AN5)

Convert

(AN7)

Convert

(AN3)

Convert

(AN4)

Convert

(AN5)

Sample/Convert Sequence 1 Sample/Convert Sequence 2

Sample

(AN6)

Sample

(AN0)

Sample

(AN1)

Sample

(AN2)

235

ADC

Interrupt

AN6

AN0

AN1

AN2

AN7

AN3

AN4

AN5

ADC1BUF0

ADC1BUF1

ADC1BUF7

Note 1: CH0-CH3 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The selected analog input

is connected to the sample capacitor.

2: On SOC Trigger, CH0-CH3 sample capacitor is disconnected from the multiplexer to simultaneously sample the analog inputs. The

analog value captured in CH0/CH1/CH2/CH3 is converted sequentially to equivalent digital counts.

3: CH0-CH3 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog input

is connected to the sample capacitor.

4: On SOC Trigger, CH0-CH3 sample capacitor is disconnected from the multiplexer to simultaneously sample the analog inputs. The

analog value captured in CH0/CH1/CH2/CH3 is converted sequentially to equivalent digital counts.

5: ADC Interrupt is generated after converting 8 samples. CH0-CH3 Input multiplexer selects analog input for sampling using MUXA

control bits (CHySA/CHyNA). The selected analog input is connected to the sample capacitor.

dsPIC33F/PIC24H Family Reference Manual

Example 16-5 shows the code sequence to set up the ADC module for Alternate Input Selection

mode in a 2-channel sequential sampling configuration for devices without DMA.

Example 16-5: Code Sequence to Set Up ADC for Alternate Input Selection for 2-Channel Sequential

Sampling (Devices without DMA)

Figure 16-16: Alternate Input Selection in 2-Channel Sequential Sampling Configuration (Devices without

DMA)

AD1CON1bits.AD12B=0; // Select 10-bit mode

AD1CON2bits.CHPS=1; // Select 2-channel mode

AD1CON2bits.SMPI = 3; // Select 4 conversion between interrupt

AD1CON1bits.ASAM = 1; // Enable Automatic Sampling

AD1CON2bits.ALTS = 1; // Enable Alternate Input Selection

AD1CON1bits.SIMSAM = 0; // Enable Sequential Sampling

AD1CON1bits.SSRC = 2; // Timer3 generates SOC trigger

// Initialize MUXA Input Selection

AD1CHS0bits.CH0SA = 6; // Select AN6 for CH0 +ve input

AD1CHS0bits.CH0NA = 0; // Select VREF- for CH0 -ve input

AD1CHS123bits.CH123SA=0;// Select AN0 for CH1 +ve input

AD1CHS123bits.CH123NA=0;// Select Vref- for CH1 -ve inputs

// Initialize MUXB Input Selection

AD1CHS0bits.CH0SB = 7; // Select AN7 for CH0 +ve input

AD1CHS0bits.CH0NB = 0; // Select VREF- for CH0 -ve input

AD1CHS123bits.CH123SB=1;// Select AN3 for CH1 +ve input

AD1CHS123bits.CH124NB=0;// Select VREF- for CH1-ve inputs

Sample

(AN6)

Sample

(AN0)

CH0

CH1

Convert

(AN6)

Convert

(AN0)

SOC

Trigger

Sample

(AN7)

Sample

(AN3)

Convert

(AN7)

Convert

(AN3)

Sample/Convert Sequence 1 Sample/Convert Sequence 2

Sample

(AN7)

Sample

(AN6)

1 2 345

ADC

Interrupt

Sample

(AN6)

Sample

(AN0)

AN6

AN0

AN7

AN3

ADC1BUF0

ADC1BUF1

ADC1BUF2

ADC1BUF3

Note 1: CH0-CH1 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The selected analog

input is connected to the sample capacitor.

2: On SOC Trigger, CH0/CH1 inputs are sequentially sampled and converted to equivalent digital counts.

3: CH0-CH1 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog

input is connected to the sample capacitor.

4: On SOC Trigger, CH0/CH1 inputs are sequentially sampled and converted to equivalent digital counts.

5: ADC Interrupt is generated after converting 4 samples. CH0-CH1 Input multiplexer selects analog input for sampling using

MUXA control bits (CHySA/CHyNA). The selected analog input is connected to the sample capacitor.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

For devices with DMA, when Alternate Input Selection mode is enabled, set SMPI<3:0> = 001

to allow two samples per DMA address point increment.

Figure 16-17: Alternate Input Selection in 4-Channel Simultaneous Sampling Configuration (Devices with

DMA)

Sample

(AN6)

Sample

(AN0)

CH0

CH1

Sample

(AN1)

Sample

(AN2)

CH2

CH3

Convert

(AN6)

Convert

(AN0)

Convert

(AN1)

SOC

Trigger

Convert

(AN2)

Sample

(AN7)

Sample

(AN3)

Sample

(AN4)

Sample

(AN5)

Convert

(AN7)

Convert

(AN3)

Convert

(AN4)

Convert

(AN5)

Sample/Convert Sequence 1 Sample/Convert Sequence 2

Sample

(AN6)

Sample

(AN0)

Sample

(AN1)

Sample

(AN2)

2 3 5

ADC

Interrupt

1 4

Note 1: CH0-CH3 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The selected analog input

is connected to the sample capacitor.

2: On SOC Trigger, CH0-CH4 sample capacitor is disconnected from the multiplexer to simultaneously sample the analog inputs. The

analog value captured in CH0/CH1/CH2/CH3 is converted sequentially to equivalent digital counts.

3: CH0-CH3 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog input

is connected to the sample capacitor.

4: On SOC Trigger, CH0-CH3 sample capacitor is disconnected from the multiplexer to simultaneously sample the analog inputs. The

analog value captured in CH0/CH1/CH2/CH3 is converted sequentially to equivalent digital counts.

5: ADC Interrupt is generated after converting every sample. CH0-CH3 Input multiplexer selects analog input for sampling using

MUXA control bits (CHySA/CHyNA). The selected analog input is connected to the sample capacitor.

5 5 5 5 5 5

AN0 Sample 1

AN1 Sample 1

AN2 Sample 1

AN3 Sample 1

AN6 Sample 1

AN4 Sample 1

AN5 Sample 1

AN7 Sample 1

AN0

Block

AN1

Block

AN2

Block

AN3

Block

AN4

Block

AN5

Block

AN6

Block

AN7

Block

dsPIC33F/PIC24H Family Reference Manual

Figure 16-18: Alternate Input Selection in 2-Channel Sequential Sampling Configuration (Devices with DMA)

16.6.3 Channel Scanning

The ADC module supports the Channel Scan mode using CH0 (S&H channel ‘0’). The number

of inputs scanned is software selectable. Any subset of the analog inputs from AN0 to AN31

(AN0-AN12 for devices without DMA) can be selected for conversion. The selected inputs are

converted in ascending order. For example, if the input selection includes AN4, AN1 and AN3,

the conversion sequence is AN1, AN3 and AN4. The conversion sequence selection is made by

programming the Channel Select register (AD1CSSL). A logic ‘1’ in the Channel Select register

marks the associated analog input channel for inclusion in the conversion sequence. The

Channel Scanning mode is enabled by setting the Channel Scan bit (CSCNA) in the ADC Control

ADC module sequences through the enabled channels.

In devices without DMA, for every sample/convert sequence, one analog input is scanned. The

ADC interrupt must be generated after all selected channels are scanned. If “N” inputs are

enabled for channel scan, an interrupt must be generated after “N” sample/convert sequence.

Table 16-13 lists the SMPI values to scan “N” analog inputs using CH0 in different ADC

configurations.

Sample

(AN6)

Sample

(AN0)

CH0

CH1

Convert

(AN6)

Convert

(AN0)

SOC

Trigger

Sample

(AN7)

Sample

(AN3)

Convert

(AN7)

Convert

(AN3)

Sample/Convert Sequence 1 Sample/Convert Sequence 2

Sample

(AN7)

Sample

(AN6)

1 2 343

ADC

Interrupt

Sample

(AN6)

Sample

(AN0)

Note 1: CH0-CH1 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The selected analog

input is connected to the sample capacitor.

2: On SOC Trigger, CH0/CH1 inputs are sequentially sampled and converted to equivalent digital counts.

3: CH0-CH1 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog

input is connected to the sample capacitor.

4: On SOC Trigger, CH0/CH1 inputs are sequentially sampled and converted to equivalent digital counts.

5: ADC Interrupt is generated after every conversion.

Note: A maximum of 16 ADC inputs (any) can be configured to be scanned at a time.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

Table 16-13: Conversions Per Interrupt in Channel Scan Mode (Devices without DMA)

Example 16-6 shows the code sequence to scan four analog inputs using CH0 in devices without

DMA. Figure 16-19 illustrates the ADC operation sequence.

Example 16-6: Code sequence to Scan four Analog Inputs Using CH0

(Devices without DMA and 10-bit/12-bit ADC)

Figure 16-19: Scan Four Analog Inputs Using CH0 (Devices without DMA)

Example 16-7 shows the code sequence to scan two analog inputs using CH0 in a 2-channel

alternate input selection configuration for devices without DMA. Figure 16-20 illustrates the ADC

operation sequence.

CHPS<1:0> SIMSAM SMPI<3:0>

(Decimal)

Conversions/

Interrupt

Description

00 x N-1 N 1-Channel mode

01 0 2N-1 2N 2-Channel Sequential Sampling

mode

1x 0 4N-1 4N 4-Channel Sequential Sampling

mode

01 1 N-1 2N 2-Channel Simultaneous Sampling

mode

1x 1 N-1 4N 4-Channel Simultaneous Sampling

mode

Note: On ADC Interrupt, the ADC internal logic is initialized to restart the conversion

sequence from the beginning.

AD1CON1bits.AD12B=1; // Select 12-bit mode, 1-channel mode

AD1CON2bits.SMPI = 3; // Select 4 conversions between interrupt

AD1CHS0bits.ASAM = 1; // Enable Automatic Sampling

AD1CON2bits.CSCNA = 1; // Enable Channel Scanning

// Initialize Channel Scan Selection

AD1CSSLbits.CSS2=1; // Enable AN2 for scan

AD1CSSLbits.CSS3=1; // Enable AN3 for scan

AD1CSSLbits.CSS5=1; // Enable AN5 for scan

AD1CSSLbits.CSS6=1; // Enable AN6 for scan

Sample

(AN2)

CH0 Convert

(AN2)

SOC

Trigger

Sample

(AN3)

Convert

(AN3)

Sample

(AN5)

Convert

(AN5)

Sample

(AN6)

Convert

(AN6)

ADC

Interrupt

dsPIC33F/PIC24H Family Reference Manual

Example 16-7: Code Sequence for Channel Scan with Alternate Input Selection (Devices without DMA)

Figure 16-20: Channel Scan with Alternate Input Selection (Devices without DMA)

AD1CON1bits.AD12B = 0; // Select 10-bit mode

AD1CON2bits.CHPS = 1; // Select 2-channel mode

AD1CON1bits.SIMSAM = 0; // Enable Sequential Sampling

AD1CON2bits.ALTS = 1; // Enable Alternate Input Selection

AD1CON2bits.CSCNA = 1; // Enable Channel Scanning

AD1CON2bits.SMPI = 7; // Select 8 conversion between interrupt

AD1CON1bits.ASAM = 1; // Enable Automatic Sampling

// Initialize Channel Scan Selection

AD1CSSLbits.CSS2 = 1; // Enable AN2 for scan

AD1CSSLbits.CSS3 = 1; // Enable AN3 for scan

// Initialize MUXA Input Selection

AD1CHS123bits.CH123SA = 0; // Select AN0 for CH1 +ve input

AD1CHS123bits.CH123NA = 0; // Select Vref- for CH1 -ve inputs

// Initialize MUXB Input Selection

AD1CHS0bits.CH0SB = 8; // Select AN8 for CH0 +ve input

AD1CHS0bits.CH0NB = 0; // Select VREF- for CH0 -ve inputs

AD1CHS123bits.CH123SB = 0; // Select AN4 for CH1 +ve input

AD1CHS123bits.CH124NB = 0; // Select VREF- for CH1 -ve inputs

Sample

(AN2)

Sample

(AN0)

CH0

CH1

Convert

(AN2)

Convert

(AN0)

SOC

Trigger

Sample

(AN8)

Sample

(AN3)

Convert

(AN8)

Convert

(AN3)

Sample

(AN8)

Sample

(AN3)

Sample

(AN3)

Sample

(AN0)

Convert

(AN3)

Convert

(AN0)

Sample

(AN8)

Sample

(AN3)

Convert

(AN8)

Convert

(AN3)

Sample

(AN8)

ADC

Trigger

Sample/Convert Sequence 1 Sample/Convert Sequence 2 Sample/Convert Sequence 3 Sample/Convert Sequence 4

123456 7 8 9

Note 1: CH0 Input multiplexer selects analog input for sampling using internally generated control bits (from Channel Scan logic) instead

of MUXA control bits. CH1 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The

selected analog input is connected to the sample capacitor.

2: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

3: CH0-CH1 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog input

is connected to the sample capacitor.

4: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

5: CH0 Input multiplexer selects analog input for sampling using internally generated control bits (from Channel Scan logic) instead

of MUXA control bits. CH1 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The

selected analog input is connected to the sample capacitor.

6: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

7: CH0-CH1 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog input

is connected to the sample capacitor.

8: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

9: ADC Interrupt is generated after converting eight samples.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

For devices with DMA, when channel scanning is used and only CH0 is active (ALTS = 0), the

SMPI<3:0> bits should be set to the number of inputs being scanned minus one (i.e.,

SMPI<3:0> = N - 1).

Figure 16-21: Scan Four Analog Inputs Using CH0 (Devices with DMA)

Figure 16-22: Channel Scan with Alternate Input Selection (Devices with DMA)

Sample

(AN2)

CH0 Convert

(AN2)

SOC

Trigger

Sample

(AN3)

Convert

(AN3)

Sample

(AN5)

Convert

(AN5)

Sample

(AN6)

Convert

(AN6)

ADC

Interrupt

Sample

(AN2)

Sample

(AN0)

CH0

CH1

Convert

(AN2)

Convert

(AN0)

SOC

Trigger

Sample

(AN8)

Sample

(AN3)

Convert

(AN8)

Convert

(AN3)

Sample

(AN8)

Sample

(AN3)

Sample

(AN3)

Sample

(AN0)

Convert

(AN3)

Convert

(AN0)

Sample

(AN8)

Sample

(AN3)

Convert

(AN8)

Convert

(AN3)

Sample

(AN8)

ADC

Trigger

Sample/Convert Sequence 1 Sample/Convert Sequence 2 Sample/Convert Sequence 3 Sample/Convert Sequence 4

1 2 3 4 5 6 7 8 9

Note 1: CH0 Input multiplexer selects analog input for sampling using internally generated control bits (from Channel Scan logic) instead

of MUXA control bits. CH1 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The

selected analog input is connected to the sample capacitor.

2: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

3: CH0-CH1 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog input

is connected to the sample capacitor.

4: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

5: CH0 Input multiplexer selects analog input for sampling using internally generated control bits (from Channel Scan logic) instead

of MUXA control bits. CH1 Input multiplexer selects analog input for sampling using MUXA control bits (CHySA/CHyNA). The

selected analog input is connected to the sample capacitor.

6: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

7: CH0-CH1 Input multiplexer selects analog input for sampling using MUXB control bits (CHySB/CHyNB). The selected analog input

is connected to the sample capacitor.

8: On SOC Trigger, CH0-CH1 inputs are sequentially sampled and converted to equivalent digital counts.

9: ADC Interrupt is generated after every conversion.

dsPIC33F/PIC24H Family Reference Manual

16.7 SPECIFYING CONVERSION RESULTS BUFFERING FOR DEVICES WITH

DMA

The ADC module contains a single-word, read-only, dual-port register (ADCxBUF0), which

stores the analog-to-digital conversion result. If more than one conversion result needs to be

buffered before triggering an interrupt, DMA data transfers can be used. Both ADC channels

(ADC1 and ADC2) can trigger a DMA data transfer. Depending on which ADC channel is

selected as the DMA IRQ source, a DMA transfer occurs when the ADC Conversion Complete

Interrupt Flag Status bit (AD1IF or AD2IF) in the Interrupt Flag Status Register (IFS0 or IFS1,

respectively) in the Interrupt Module gets set as a result of a sample conversion sequence.

The result of every analog-to-digital conversion is stored in the ADCxBUF0 register. If a DMA

channel is not enabled for the ADC module, each result should be read by the user application

before it gets overwritten by the next conversion result. However, if DMA is enabled, multiple con-

version results can be automatically transferred from ADCxBUF0 to a user-defined buffer in the

DMA RAM area. Thus, the application can process several conversion results with minimal soft-

ware overhead.

The DMA Buffer Build Mode bit (ADDMABM) in ADCx Control Register 1 (ADxCON1<12>) deter-

mines how the conversion results are filled in the DMA RAM buffer area being used for the ADC.

If this bit is set (ADDMABM = 1), DMA buffers are written in the order of conversion. The ADC

module provides an address to the DMA channel that is the same as the address used for the

non-DMA stand-alone buffer. If the ADDMABM bit is cleared, then DMA buffers are written in

Scatter/Gather mode. The ADC module provides a Scatter/Gather address to the DMA channel,

based on the index of the analog input and the size of the DMA buffer.

When the SIMSAM bit specifies simultaneous sampling, the number of data samples in the buffer

is related to the CHPS<1:0> bits. Algorithmically, the channels per sample (CH/S) times the num-

ber of samples results in the number of data sample entries in the buffer. To avoid loss of data in

the buffer due to overruns, the DMAxCNT register must be set to the desired buffer size.

When the ADC module is simultaneously sampling two or more ADC channels and CH0 is in

channel scanning mode, there is a limit of 16 conversions, after which time the ADC module

restarts conversion from the first ADC input in CH0. When operating the ADC module in this

mode, the DMAxCNT register must be set to 15 to avoid data loss due to buffer overrun.

Disabling the ADC interrupt is not done with the SMPI<3:0> bits. To disable the interrupt, clear

the ADxIE analog module interrupt enable bit.

16.7.1 Using DMA in the Scatter/Gather Mode

When the ADDMABM bit is ‘0’, the Scatter/Gather mode is enabled. In this mode, the DMA chan-

nel must be configured for Peripheral Indirect Addressing. The DMA buffer is divided into con-

secutive memory blocks corresponding to all available analog inputs (out of AN0 - AN31). Each

conversion result for a particular analog input is automatically transferred by the ADC module to

the corresponding block within the user-defined DMA buffer area. Successive samples for the

same analog input are stored in sequence within the block assigned to that input.

The number of samples that need to be stored in the DMA buffer for each analog input is

specified by the DMABL<2:0> bits (ADxCON4<2:0>).

The buffer locations within each block are accessed by the ADC module using an internal pointer,

which is initialized to ‘0’ when the ADC module is enabled. When this internal pointer reaches

the value defined by the DMABL<2:0> bits, it gets reset to ‘0’. This ensures that conversion

results of one analog input do not corrupt the conversion results of other analog inputs. The rate

at which this internal pointer is incremented when data is written to the DMA buffer is specified

by the SMPI<3:0> bits.

Note: For information about how to configure a DMA channel to transfer data from the

ADC buffer and define a corresponding DMA buffer area from where the data can

be accessed by the application, please refer to Section 22. “Direct Memory

Access (DMA)” (DS70182). For specific information about the Interrupt registers,

please refer to Section 6. “Interrupts” (DS70184).

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

When no channel scanning or alternate sampling is required, SMPI<3:0> should be cleared,

implying that the pointer will increment on every sample per channel. Thus, it is theoretically pos-

sible to use every location in the DMA buffer for the blocks assigned to the analog inputs being

sampled.

In the example illustrated in Figure 16-23, it can be observed that the conversion results for the

AN0, AN1 and AN2 inputs are stored in sequence, leaving no unused locations in their

corresponding memory blocks. However, for the four analog inputs (AN4, AN5, AN6 and AN7)

that are scanned by CH0, the first location in the AN5 block, the first two locations in the AN6

block and the first three locations in the AN7 block are unused, resulting in a relatively inefficient

arrangement of data in the DMA buffer.

When scanning is used, and no simultaneous sampling is performed (SIMSAM = 0), SMPI<3:0>

should be set to one less than the number of inputs being scanned. For example, if CHPS<1:0> = 00

(only one S&H channel is used), and AD1CSSL = 0xFFFF, indicating that AN0-AN15 are being

scanned, then set SMPI<3:0> = 1111 so that the internal pointer is incremented only after every

sixteenth sample/conversion sequence. This avoids unused locations in the blocks corresponding to

the analog inputs being scanned.

Similarly, if ALTS = 1, indicating that alternating analog input selections are used, then

SMPI<3:0> is set to ‘0001’, thereby incrementing the internal pointer after every second sample.

Note: The ADC module does not perform limit checks on the generated buffer addresses.

For example, you must ensure that the Least Significant bits (LSbs) of the DMAx-

STA or DMAxSTB register used are indeed ‘0’. Also, the number of potential analog

inputs multiplied by the buffer size specified by DMABL<2:0> must not exceed the

total length of the DMA buffer.

dsPIC33F/PIC24H Family Reference Manual

Figure 16-23: DMA Buffer in Scatter/Gather Mode

DMAxSTA AN0 – SAMPLE 1

AN0 – SAMPLE 2

AN0 – SAMPLE 3

AN0 – SAMPLE 4

AN0 – SAMPLE 5

AN0 – SAMPLE 6

AN0 – SAMPLE 7

AN0 – SAMPLE 8

AN1 – SAMPLE 1

AN1 – SAMPLE 2

AN1 – SAMPLE 3

AN1 – SAMPLE 4

AN1 – SAMPLE 5

AN1 – SAMPLE 6

AN1 – SAMPLE 7

AN1 – SAMPLE 8

AN2 – SAMPLE 1

AN2 – SAMPLE 2

AN2 – SAMPLE 3

AN2 – SAMPLE 4

AN2 – SAMPLE 5

AN2 – SAMPLE 6

AN2 – SAMPLE 7

AN2 – SAMPLE 8

—

AN4 – SAMPLE 1

—

AN4 – SAMPLE 5

—

AN5 – SAMPLE 2

—

AN5 – SAMPLE 6

—

AN6 – SAMPLE 3

—

AN6 – SAMPLE 7

—

AN7 – SAMPLE 4

—

AN7 – SAMPLE 8

—

AN0 BLOCK

AN1 BLOCK

AN2 BLOCK

AN3 BLOCK

AN4 BLOCK

AN5 BLOCK

AN6 BLOCK

AN7 BLOCK

AN31 BLOCK

{

Unused Buffer Locations

{

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.7.2 Using DMA in the Conversion Order Mode

When the ADDMABM bit (ADCON1<12>) = 1, the Conversion Order mode is enabled. In this

mode, the DMA channel can be configured for Register Indirect or Peripheral Indirect

Addressing. All conversion results are stored in the user-specified DMA buffer area in the same

order in which the conversions are performed by the ADC module. In this mode, the buffer is not

divided into blocks allocated to different analog inputs. Rather the conversion results from

different inputs are interleaved according to the specific buffer fill modes being used.

In this configuration, the buffer pointer is always incremented by one word. In this case, the

SMPI<3:0> bits (ADxCON2<5:2>) must be cleared and the DMABL<2:0> bits (ADxCON4<2:0>)

are ignored.

Figure 16-24 illustrates an example identical to the configuration in Figure 16-23, but using the

Conversion Order mode. In this example, the DMAxCNT register has been configured to

generate the DMA interrupt after 16 conversion results have been obtained.

Figure 16-24: DMA Buffer in Conversion Order Mode

AN4 – SAMPLE 1

DMAxSTA

AN0 – SAMPLE 1

AN1 – SAMPLE 1

AN2 – SAMPLE 1

AN5 – SAMPLE 2

AN0 – SAMPLE 2

AN1 – SAMPLE 2

AN2 – SAMPLE 2

AN6 – SAMPLE 3

AN0 – SAMPLE 3

AN1 – SAMPLE 3

AN2 – SAMPLE 3

AN7 – SAMPLE 4

AN0 – SAMPLE 4

AN1 – SAMPLE 4

AN2 – SAMPLE 4

dsPIC33F/PIC24H Family Reference Manual

16.8 ADC CONFIGURATION EXAMPLE

The following steps should be used for performing an analog-to-digital conversion:

1. Select 10-bit or 12-bit mode (ADxCON1<10>).

2. Select the voltage reference source to match the expected range on analog inputs

(ADxCON2<15:13>).

3. Select the analog conversion clock to match the desired data rate with processor clock

(ADxCON3<7:0>).

4. Select the port pins as analog inputs (ADxPCFGH<15:0> and ADxPCFGL<15:0>).

5. Determine how inputs will be allocated to Sample and Hold channels (ADxCHS0<15:0>

and ADxCHS123<15:0>).

6. Determine how many Sample and Hold channels will be used (ADxCON2<9:8>,

ADxPCFGH<15:0> and ADxPCFGL<15:0>).

7. Determine how sampling will occur (ADxCON1<3>, ADxCSSH<15:0> and

ADxCSSL<15:0>).

8. Select Manual or Auto Sampling.

9. Select the conversion trigger and sampling time.

10. Select how the conversion results are stored in the buffer (ADxCON1<9:8>).

11. Select the interrupt rate or DMA buffer pointer increment rate (ADxCON2<9:5>).

12. Select the number of samples in DMA buffer for each ADC module input

(ADxCON4<2:0>).

13. Select the data format.

14. Configure the ADC interrupt (if required):

• Clear the ADxIF bit

• Select interrupt priority (ADxIP<2:0>)

• Set the ADxIE bit

15. Configure the DMA channel (if needed).

16. Turn on the ADC module (ADxCON1<15>).

The options for these configuration steps are described in subsequent sections.

dsPIC33F/PIC24H Family Reference Manual

Example 16-8: ADC Configuration Code for 1.1 Msps

void initAdc1(void)

{

AD1CON1bits.FORM = 3; // Data Output Format: Signed Fraction (Q15 format)

AD1CON1bits.SSRC = 7; // Internal Counter (SAMC) ends sampling and starts conversion

AD1CON1bits.ASAM = 1; // ADC Sample Control: Sampling begins immediately after

// conversion

AD1CON1bits.AD12B = 0; // 10-bit ADC operation

AD1CON2bits.SIMSAM = 0; // Sequential sampling of channels

AD1CON2bits.CHPS = 1; // Converts channels CH0/CH1

AD1CON3bits.ADRC = 0; // ADC Clock is derived from Systems Clock

AD1CON3bits.SAMC = 0; // Auto Sample Time = 0 * TAD

AD1CON3bits.ADCS = 2; // ADC Conversion Clock T = T * (ADCS + 1) = (1/40M) * 3 = AD CY

// 75 ns (13.3 MHz)

// ADC Conversion Time for 10-bit Tconv = 12 * TAD = 900 ns (1.1 MHz)

AD1CON1bits.ADDMABM = 1; // DMA buffers are built in conversion order mode

AD1CON2bits.SMPI = 0; // SMPI must be 0

//AD1CHS0/AD1CHS123: Analog-to-Digital Input Select Register

AD1CHS0bits.CH0SA = 0; // MUXA +ve input selection (AIN0) for CH0

AD1CHS0bits.CH0NA = 0; // MUXA -ve input selection (VREF-) for CH0

AD1CHS123bits.CH123SA = 0; // MUXA +ve input selection (AIN0) for CH1

AD1CHS123bits.CH123NA = 0; // MUXA -ve input selection (VREF-) for CH1

//AD1PCFGH/AD1PCFGL: Port Configuration Register

AD1PCFGL = 0xFFFF;

AD1PCFGH = 0xFFFF;

AD1PCFGLbits.PCFG0 = 0; // AN0 as Analog Input

IFS0bits.AD1IF = 0; // Clear the Analog-to-Digital interrupt flag bit

IEC0bits.AD1IE = 0; // Do Not Enable Analog-to-Digital interrupt

AD1CON1bits.ADON = 1; // Turn on the ADC

void initDma0(void)

{

DMA0CONbits.AMODE = 0; // Configure DMA for Register indirect with post increment

DMA0CONbits.MODE = 2; // Configure DMA for Continuous Ping-Pong mode

DMA0PAD = (int)&ADC1BUF0;

DMA0CNT = (NUMSAMP-1);

DMA0REQ = 13;

DMA0STA = __builtin_dmaoffset(BufferA);

DMA0STB = __builtin_dmaoffset(BufferB);

IFS0bits.DMA0IF = 0; //Clear the DMA interrupt flag bit

IEC0bits.DMA0IE = 1; //Set the DMA interrupt enable bit

DMA0CONbits.CHEN = 1;

}

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.10 SAMPLE AND CONVERSION SEQUENCE EXAMPLES FOR DEVICES

WITHOUT DMA

The following configuration examples show the analog-to-digital operation in different sampling

and buffering configurations. In each example, setting the ASAM bit starts automatic sampling.

A conversion trigger ends sampling and starts conversion.

16.10.1 Sampling and Converting a Single Channel Multiple Times

Figure 16-26 Table 16-14 and illustrate a basic configuration of the ADC. In this case, one ADC

input, AN0, is sampled by one S&H channel, CH0, and converted. The results are stored in the

ADC buffer (ADC1BUF0-ADC1BUFF). This process repeats 16 times until the buffer is full and

then the ADC module generates an interrupt. The entire process then repeats.

The CHPS bits specify that only S&H CH0 is active. With ALTS clear, only the MUXA inputs are

active. The CH0SA bits and CH0NA bit are specified (AN0-VREF-) as the input to the S&H

channel. All other input selection bits are not used.

Figure 16-26: Converting One Channel 16 Times/Interrupt

ADC Clock

SAMP

ADC1BUF0

TSAMP

TCONV

ADC1BUF1

DONE

ADC1BUF2

ADC1BUFF

Input to CH0 AN0

TSAMP

TCONV

AN0

TSAMP

TCONV

AN0

TSAMP

TCONV

AN0

AD1IF

ASAM

Conversion

Trigger

dsPIC33F/PIC24H Family Reference Manual

Table 16-14: Converting One Channel 16 Times per ADC Interrupt

CONTROL BITS OPERATION SEQUENCE

Sequence Select Sample MUXA Inputs: AN0 → CH0

SMPI<3:0> = 1111 Convert CH0, Write ADC1BUF0

Interrupt on 16th sample Sample MUXA Inputs: AN0 → CH0

CHPS<1:0> = 00 Convert CH0, Write ADC1BUF1

Sample Channel CH0 Sample MUXA Inputs: AN0 → CH0

SIMSAM = n/a Convert CH0, Write ADC1BUF2

Not applicable for single channel sample Sample MUXA Inputs: AN0 → CH0

BUFM = 0Convert CH0, Write ADC1BUF3

Single 16-word result buffer Sample MUXA Inputs: AN0 → CH0

ALTS = 0 Convert CH0, Write ADC1BUF4

Always use MUXA input select Sample MUXA Inputs: AN0 → CH0

MUXA Input Select Convert CH0, Write ADC1BUF5

CH0SA<3:0> = 0000 Sample MUXA Inputs: AN0 → CH0

Select AN0 for CH0+ input Convert CH0, Write ADC1BUF6

CH0NA = 0Sample MUXA Inputs: AN0 → CH0

Select VREF- for CH0- input Convert CH0, Write ADC1BUF7

CSCNA = 0Sample MUXA Inputs: AN0 → CH0

No input scan Convert CH0, Write ADC1BUF8

CSSL<15:0> = n/a Sample MUXA Inputs: AN0 → CH0

Scan input select unused Convert CH0, Write ADC1BUF9

CH123SA = n/a Sample MUXA Inputs: AN0 → CH0

Channel CH1, CH2, CH3 + input unused Convert CH0, Write ADC1BUFA

CH123NA<1:0> = n/a Sample MUXA Inputs: AN0 → CH0

Channel CH1, CH2, CH3 - input unused Convert CH0, Write ADC1BUFB

MUXB Input Select Sample MUXA Inputs: AN0 → CH0

CH0SB<3:0> = n/a Convert CH0, Write ADC1BUFC

Channel CH0+ input unused Sample MUXA Inputs: AN0 → CH0

CH0NB = n/a Convert CH0, Write ADC1BUFD

Channel CH0- input unused Sample MUXA Inputs: AN0 → CH0

CH123SB = n/a Convert CH0, Write ADC1BUFE

Channel CH1, CH2, CH3 + input unused Sample MUXA Inputs: AN0 → CH0

CH123NB<1:0> = n/a Convert CH0, Write ADC1BUFF

Channel CH1, CH2, CH3 - input unused ADC Interrupt

Repeat

ADC Buffer @

First ADC Interrupt

ADC Buffer @

Second ADC Interrupt

ADC1BUF0 AN0 Sample 1 AN0 Sample 17

ADC1BUF1 AN0 Sample 2 AN0 Sample 18

ADC1BUF2 AN0 Sample 3 AN0 Sample 19

ADC1BUF3 AN0 Sample 4 AN0 Sample 20

ADC1BUF4 AN0 Sample 5 AN0 Sample 21

ADC1BUF5 AN0 Sample 6 AN0 Sample 22

ADC1BUF6 AN0 Sample 7 AN0 Sample 23

ADC1BUF7 AN0 Sample 8 AN0 Sample 24

ADC1BUF8 AN0 Sample 9 AN0 Sample 25

ADC1BUF9 AN0 Sample 10 AN0 Sample 26

ADC1BUFA AN0 Sample 11 AN0 Sample 27

ADC1BUFB AN0 Sample 12 AN0 Sample 28

ADC1BUFC AN0 Sample 13 AN0 Sample 29

ADC1BUFD AN0 Sample 14 AN0 Sample 30

ADC1BUFE AN0 Sample 15 AN0 Sample 31

ADC1BUFF AN0 Sample 16 AN0 Sample 32

dsPIC33F/PIC24H Family Reference Manual

Table 16-15: Scanning Through 16 Inputs per ADC Interrupt

CONTROL BITS OPERATION SEQUENCE

Sequence Select Sample MUXA Inputs: AN0 → CH0

SMPI<3:0> = 1111 Convert CH0, Write ADC1BUF0

Interrupt on 16th sample Sample MUXA Inputs: AN1 → CH0

CHPS<1:0> = 00 Convert CH0, Write ADC1BUF1

Sample Channel CH0 Sample MUXA Inputs: AN2 → CH0

SIMSAM = n/a Convert CH0, Write ADC1BUF2

Not applicable for single channel sample Sample MUXA Inputs: AN3 → CH0

BUFM = 0Convert CH0, Write ADC1BUF3

Single 16-word result buffer Sample MUXA Inputs: AN4 → CH0

ALTS = 0Convert CH0, Write ADC1BUF4

Always use MUXA input select Sample MUXA Inputs: AN5 → CH0

MUXA Input Select Convert CH0, Write ADC1BUF5

CH0SA<3:0> = n/a Sample MUXA Inputs: AN6 → CH0

Over-ride by CSCNA Convert CH0, Write ADC1BUF6

CH0NA = 0Sample MUXA Inputs: AN7 → CH0

Select VREF- for CH0- input Convert CH0, Write ADC1BUF7

CSCNA = 1Sample MUXA Inputs: AN8 → CH0

Scan CH0+ Inputs Convert CH0, Write ADC1BUF8

CSSL<15:0> = 1111 1111 1111 1111 Sample MUXA Inputs: AN9 → CH0

Scan input select unused Convert CH0, Write ADC1BUF9

CH123SA = n/a Sample MUXA Inputs: AN10 → CH0

Channel CH1, CH2, CH3 + input unused Convert CH0, Write ADC1BUFA

CH123NA<1:0> = n/a Sample MUXA Inputs: AN11 → CH0

Channel CH1, CH2, CH3 - input unused Convert CH0, Write ADC1BUFB

MUXB Input Select Sample MUXA Inputs: AN12 → CH0

CH0SB<3:0> = n/a Convert CH0, Write ADC1BUFC

Channel CH0+ input unused Sample MUXA Inputs: AN13 → CH0

CH0NB = n/a Convert CH0, Write ADC1BUFD

Channel CH0- input unused Sample MUXA Inputs: AN14 → CH0

CH123SB = n/a Convert CH0, Write ADC1BUFE

Channel CH1, CH2, CH3 + input unused Sample MUXA Inputs: AN15 → CH0

CH123NB<1:0> = n/a Convert CH0, Write ADC1BUFF

Channel CH1, CH2, CH3 - input unused ADC Interrupt

Repeat

ADC Buffer @

First ADC Interrupt

ADC Buffer @

Second ADC Interrupt

ADC1BUF0 AN0 Sample 1 AN0 Sample 17

ADC1BUF1 AN1 Sample 2 AN1 Sample 18

ADC1BUF2 AN2 Sample 3 AN2 Sample 19

ADC1BUF3 AN3 Sample 4 AN3 Sample 20

ADC1BUF4 AN4 Sample 5 AN4 Sample 21

ADC1BUF5 AN5 Sample 6 AN5 Sample 22

ADC1BUF6 AN6 Sample 7 AN6 Sample 23

ADC1BUF7 AN7 Sample 8 AN7 Sample 24

ADC1BUF8 AN8 Sample 9 AN8 Sample 25

ADC1BUF9 AN9 Sample 10 AN9 Sample 26

ADC1BUFA AN10 Sample 11 AN10 Sample 27

ADC1BUFB AN11 Sample 12 AN11 Sample 28

ADC1BUFC AN12 Sample 13 AN12 Sample 29

ADC1BUFD AN13 Sample 14 AN13 Sample 30

ADC1BUFE AN14 Sample 15 AN14 Sample 31

ADC1BUFF AN15 Sample 16 AN15 Sample 32

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.10.3 Sampling Three Inputs Frequently While Scanning Four Other

Inputs

Figure 16-28 and Table 16-16 illustrate how the ADC module could be configured to sample

three inputs frequently using S&H channe57

ls CH1, CH2 and CH3; while four other inputs are sampled less frequently by scanning them

using S&H channel CH0. In this case, only MUXA inputs are used, and all four channels are

sampled simultaneously. Four different inputs (AN4, AN5, AN6, AN7) are scanned in CH0,

whereas AN0, AN1 and AN2 are the fixed inputs for CH1, CH2 and CH3, respectively. Thus, in

every set of 16 samples, AN0, AN1 and AN2 are sampled four times, while AN4, AN5, AN6 and

AN7 are sampled only once each.

Figure 16-28: Converting Three Inputs, Four Times and Four Inputs, One Time/Interrupt

ADC Clock

SAMP

DONE

Input to CH0 AN4

TSAMP

AD1IF

TCONVTCONVTCONVTCONV

AN0

AN1

AN2

Input to CH1

Input to CH2

Input to CH3

ADC1BUFD

ADC1BUFE

ADC1BUFF

AN5

TSAMP

AN0

AN1

AN2

AN7

TSAMP

AN0

AN1

AN2

ASAM

AN4

AN0

AN1

AN2

ADC1BUF0

ADC1BUF1

ADC1BUF2

ADC1BUF3

ADC1BUFC

AN6

AN0

AN1

AN2

Conversion

Trigger

TCONVTCONVTCONVTCONV TCONVTCONVTCONVTCONV

dsPIC33F/PIC24H Family Reference Manual

Table 16-16: Converting Three Inputs, Four Times and Four Inputs, One Time per ADC Interrupt

CONTROL BITS OPERATION SEQUENCE

Sequence Select Sample MUXA Inputs:

SMPI<3:0> = 0011 AN4 → CH0, AN0 → CH1, AN1 → CH2, AN2 → CH3

Interrupt on 4th sample Convert CH0, Write ADC1BUF0

CHPS<1:0> = 1X Convert CH1, Write ADC1BUF1

Sample Channels CH0, CH1, CH2, CH3 Convert CH2, Write ADC1BUF2

SIMSAM = 1Convert CH3, Write ADC1BUF3

Sample all channels simultaneously Sample MUXA Inputs:

BUFM = 0AN5 → CH0, AN0 → CH1, AN1 → CH2, AN2 → CH3

Single 16-word result buffer Convert CH0, Write ADC1BUF4

ALTS = 0Convert CH1, Write ADC1BUF5

Always use MUXA input select Convert CH2, Write ADC1BUF6

MUXA Input Select Convert CH3, Write ADC1BUF7

CH0SA<3:0> = n/a Sample MUXA Inputs:

Over-ride by CSCNA AN6 → CH0, AN0 → CH1, AN1 → CH2, AN2 → CH3

CH0NA = 0Convert CH0, Write ADC1BUF8

Select VREF- for CH0- input Convert CH1, Write ADC1BUF9

CSCNA = 1Convert CH2, Write ADC1BUF10

Scan CH0+ Inputs Convert CH3, Write ADC1BUF11

CSSL<15:0> = 0000 0000 1111 0000 Sample MUXA Inputs:

Scan AN4, AN5, AN6, AN7 AN7 → CH0, AN0 → CH1, AN1 → CH2, AN2 → CH3

CH123SA = 0Convert CH0, Write ADC1BUFC

CH1+ = AN0, CH2+ = AN1, CH3+ = AN2 Convert CH1, Write ADC1BUFD

CH123NA<1:0> = 0X Convert CH2, Write ADC1BUFE

CH1-,CH2-,CH3- = VREF- Convert CH3, Write ADC1BUFF

MUXB Input Select ADC Interrupt

CH0SB<3:0> = n/a Repeat

Channel CH0+ input unused

CH0NB = n/a

Channel CH0- input unused

CH123SB = n/a

Channel CH1, CH2, CH3 + input unused

CH123NB<1:0> = n/a

Channel CH1, CH2, CH3 - input unused

ADC Buffer @

First ADC Interrupt

ADC Buffer @

Second ADC Interrupt

ADC1BUF0 AN4 Sample 1 AN4 Sample 2

ADC1BUF1 AN0 Sample 1 AN0 Sample 5

ADC1BUF2 AN1 Sample 1 AN1 Sample 5

ADC1BUF3 AN2 Sample 1 AN2 Sample 5

ADC1BUF4 AN5 Sample 1 AN5 Sample 2

ADC1BUF5 AN0 Sample 2 AN0 Sample 6

ADC1BUF6 AN1 Sample 2 AN1 Sample 6

ADC1BUF7 AN2 Sample 2 AN2 Sample 6

ADC1BUF8 AN6 Sample 1 AN6 Sample 2

ADC1BUF9 AN0 Sample 3 AN0 Sample 7

ADC1BUFA AN1 Sample 3 AN1 Sample 7

ADC1BUFB AN2 Sample 3 AN2 Sample 7

ADC1BUFC AN7 Sample 1 AN7 Sample 2

ADC1BUFD AN0 Sample 4 AN0 Sample 8

ADC1BUFE AN1 Sample 4 AN1 Sample 8

ADC1BUFF AN2 Sample 4 AN2 Sample 8

Note: In this instance of simultaneous sampling, one sample and four conversions are treated as one sample

and convert sequence. Therefore, when SMPI<3:0> = 0011, an ADC interrupt is generated after

16 samples are converted and buffered in ADC1BUF0-ADC1BUFF.

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.10.5 Sampling Eight Inputs Using Simultaneous Sampling

This and the next example demonstrate identical setups with the exception that this example

uses simultaneous sampling (SIMSAM = 1), and the following example uses sequential sampling

(SIMSAM = 0). Both examples use alternating inputs and specify differential inputs to the S&H.

Figure 16-30 and Table 16-18 demonstrate simultaneous sampling. When converting more than

one channel and selecting simultaneous sampling, the ADC module samples all channels, then

performs the required conversions in sequence. In this example, with ASAM set, sampling begins

after the conversions complete.

Figure 16-30: Sampling Eight Inputs Using Simultaneous Sampling

ADC Clock

SAMP

DONE

Input to CH0 AN13-AN1

TSAMP

AD1IF

AN0

AN1

AN2

Input to CH1

Input to CH2

Input to CH3

ADC1BUFD

ADC1BUFE

ADC1BUFF

AN14

TSAMP

AN3-AN6

AN4-AN7

AN5-AN8

AN14

TSAMP

AN3-AN6

AN4-AN7

AN5-AN8

ASAM

AN13-AN1

AN0

AN1

AN2

ADC1BUF0

ADC1BUF1

ADC1BUF2

ADC1BUF3

ADC1BUFC

Conversion

Trigger

TCONVTCONVTCONVTCONV TCONVTCONVTCONVTCONV TCONVTCONVTCONVTCONV

dsPIC33F/PIC24H Family Reference Manual

Table 16-18: Sampling Eight Inputs Using Simultaneous Sampling

CONTROL BITS OPERATION SEQUENCE

Sequence Select Sample MUXA Inputs:

SMPI<3:0> = 0001 (AN13-AN1) → CH0, AN0 → CH1, AN1 → CH2, AN2 → CH3

Interrupt on 2nd sample Convert CH0, Write ADC1BUF0

CHPS<1:0> = 1X Convert CH1, Write ADC1BUF1

Sample Channels CH0, CH1, CH2, CH3 Convert CH2, Write ADC1BUF2

SIMSAM = 1Convert CH3, Write ADC1BUF3

Sample all channels simultaneously Sample MUXB Inputs:

BUFM = 0AN14 → CH0,

Single 16-word result buffer (AN3-AN6) → CH1, (AN4-AN7) → CH2, (AN5-AN8) → CH3

ALTS = 1Convert CH0, Write ADC1BUF4

Alternate MUXA/MUXB input select Convert CH1, Write ADC1BUF5

MUXA Input Select Convert CH2, Write ADC1BUF6

CH0SA<3:0> = 1101 Convert CH3, Write ADC1BUF7

Select AN13 for CH0+ input Sample MUXA Inputs:

CH0NA = 1(AN13-AN1) → CH0, AN0 → CH1, AN1 → CH2, AN2 → CH3

Select AN1 for CH0- input Convert CH0, Write ADC1BUF8

CSCNA = 0Convert CH1, Write ADC1BUF9

No input scan Convert CH2, Write ADC1BUFA

CSSL<15:0> = n/a Convert CH3, Write ADC1BUFB

Scan input select unused Sample MUXB Inputs:

CH123SA = 0AN14→ CH0,

CH1+ = AN0, CH2+ = AN1, CH3+ = AN2 (AN3-AN6) → CH1, (AN4-AN7) → CH2, (AN5-AN8) → CH3

CH123NA<1:0> = 0X Convert CH0, Write ADC1BUFC

CH1-, CH2-, CH3- = VREF- Convert CH1, Write ADC1BUFD

MUXB Input Select Convert CH2, Write ADC1BUFE

CH0SB<3:0> = 1110 Convert CH3, Write ADC1BUFF

Select AN14 for CH0+ input ADC Interrupt

CH0NB = 0Repeat

Select VREF- for CH0- input

CH123SB = 1

CH1+ = AN3, CH2+ = AN4, CH3+ = AN5

CH123NB<1:0> = 10

CH1- = AN6, CH2- = AN7, CH3- = AN8

ADC Buffer @

First ADC Interrupt

ADC Buffer @

Second ADC Interrupt

ADC1BUF0 (AN13-AN1) Sample 1 (AN13-AN1) Sample 3

ADC1BUF1 AN0 Sample 1 AN0 Sample 3

ADC1BUF2 AN1 Sample 1 AN1 Sample 3

ADC1BUF3 AN2 Sample 1 AN2 Sample 3

ADC1BUF4 AN14 Sample 1 AN14 Sample 3

ADC1BUF5 (AN3-AN6) Sample 1 (AN3-AN6) Sample 3

ADC1BUF6 (AN4-AN7) Sample 1 (AN4-AN7) Sample 3

ADC1BUF7 (AN5-AN8) Sample 1 (AN5-AN8) Sample 3

ADC1BUF8 (AN13-AN1) Sample 2 (AN13-AN1) Sample 4

ADC1BUF9 AN0 Sample 2 AN0 Sample 4

ADC1BUFA AN1 Sample 2 AN1 Sample 4

ADC1BUFB AN2 Sample 2 AN2 Sample 4

ADC1BUFC AN14 Sample 2 AN14 Sample 4

ADC1BUFD (AN3-AN6) Sample 2 (AN3-AN6) Sample 4

ADC1BUFE (AN4-AN7) Sample 2 (AN4-AN7) Sample 4

ADC1BUFF (AN5-AN8) Sample 2 (AN5-AN8) Sample 4

Section 16. Analog-to-Digital Converter (ADC)

Analog-to-Digital

Converter (ADC)

16.10.6 Sampling Eight Inputs Using Sequential Sampling

Figure 16-31 and Table 16-19 demonstrate sequential sampling. When converting more than

one channel and selecting sequential sampling, the ADC module starts sampling a channel at

the earliest opportunity, then performs the required conversions in sequence. In this example,

with ASAM set, sampling of a channel begins after the conversion of that channel completes.

When ASAM is clear, sampling does not resume after conversion completion but occurs when

the SAMP bit is set.

When utilizing more than one channel, sequential sampling provides more sampling time since

a channel can be sampled while conversion occurs on another.

Figure 16-31: Sampling Eight Inputs Using Sequential Sampling

ADC Clock

SAMP

DONE

Input to CH0 AN13-AN1

TSAMP

AD1IF

AN0

AN1

AN2

Input to CH1

Input to CH2

Input to CH3

ADC1BUFD

ADC1BUFE

ADC1BUFF

AN14

TSAMP

AN4-AN7

AN5-AN8

AN14

TSAMP

AN3-AN6

AN4-AN7

AN5-AN8

ASAM

AN1

AN2

ADC1BUF0

ADC1BUF1

ADC1BUF2

ADC1BUF3

ADC1BUFC

AN13-AN1

AN0

AN2

Conversion

Trigger

TCONVTCONVTCONVTCONV TCONVTCONVTCONVTCONV TCONVTCONVTCONVTCONV

AN3-AN6

AN1

AN13-AN1

AN0

Produkt Specifikationer

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