PIC18LF4331-ESLASHML datasheet(247/392 Pages) MICROCHIP

247 / 392 page

 2010 Microchip Technology Inc.

DS39616D-page 247

PIC18F2331/2431/4331/4431

21.1

Configuring the A/D Converter

The A/D Converter has two types of conversions, two

modes of operation and eight different Sequencing

modes. These features are controlled by the ACONV

bit (ADCON0<5>), ACSCH bit (ADCON0<4>) and

ACMOD<1:0> bits (ADCON0<3:2>). In addition, the

A/D channels are divided into four groups as defined

in the ADCHS register. Table 21-1 shows the

sequence configurations as controlled by the ACSCH

and ACMOD<1:0> bits.

21.1.1

CONVERSION TYPE

Two types of conversions exist in the high-speed 10-bit

A/D Converter module that are selected using the

ACONV bit. Single-Shot mode allows a single conversion

or sequence to be enabled when ACONV = 0. At the end

of the sequence, the GO/DONE bit will be automatically

cleared and the interrupt flag, ADIF, will be set. When

using

Single-Shot

mode

and

configured

for

Simultaneous mode, STNM2, acquisition time must be

used to ensure proper conversion of the analog input

signals.

Continuous Loop mode allows the defined sequence to

be executed in a continuous loop when ACONV = 1. In

this mode, either the user can trigger the start of

conversion by setting the GO/DONE bit, or one of the

A/D triggers can start the conversion. The interrupt flag,

ADIF, is set based on the configuration of the bits,

ADRS<1:0> (ADCON3<7:6>). In Simultaneous modes,

STNM1 and STNM2 acquisition time must be config-

ured to ensure proper conversion of the analog input

signals.

21.1.2

CONVERSION MODE

The ACSCH bit (ADCON0<4>) controls how many

channels are used in the configured sequence. When

clear, the A/D is configured for single channel conver-

sion and will convert the group selected by the

ACMOD<1:0> bits and the channel selected by the

GxSEL<1:0> bits (ADCHS register). When ACSCH = 1,

the A/D is configured for multiple channel conversion

and the sequence is defined by ACMOD<1:0>.

TABLE 21-1:

AUTO-CONVERSION SEQUENCE CONFIGURATIONS

Mode

ACSCH

ACMOD<1:0>

Description

Multi-Channel Sequential Mode 1

(SEQM1)

100

Groups A and B are sampled and converted

sequentially.

Multi-Channel Sequential Mode 2

(SEQM2)

101

Groups A, B, C and D are sampled and converted

sequentially.

Multi-Channel Simultaneous Mode 1

(STNM1)

110

Groups A and B are sampled simultaneously and

converted sequentially.

Multi-Channel Simultaneous Mode 2

(STNM2)

111

Groups A and B are sampled simultaneously, then

converted sequentially. Then, Group C and D are

sampled simultaneously, then converted

sequentially.

Single Channel Mode 1 (SCM1)

000

Group A is sampled and converted.

Single Channel Mode 2 (SCM2)

001

Group B is sampled and converted.

Single Channel Mode 3 (SCM3)

010

Group C is sampled and converted.

Single Channel Mode 4 (SCM4)

011

Group D is sampled and converted.

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