PIC16F87-ISLASHML datasheet(118/214 Pages) MICROCHIP

118 / 214 page

PIC16F87/88

DS30487B-page 116

Preliminary

 2003 Microchip Technology Inc.

The ADRESH:ADRESL registers contain the result of

the A/D conversion. When the A/D conversion is com-

plete, the result is loaded into the A/D result register

pair, the GO/DONE bit (ADCON0<2>) is cleared, and

A/D Interrupt Flag bit, ADIF, is set. The block diagram

of the A/D module is shown in Figure 12-1.

After the A/D module has been configured as desired,

the selected channel must be acquired before the con-

version is started. The analog input channels must

have their corresponding TRIS bits selected as inputs.

To determine sample time, see Section 12.1. After this

sample time has elapsed, the A/D conversion can be

started.

These steps should be followed for doing an A/D

conversion:

Configure the A/D module:

• Configure analog/digital I/O (ANSEL)

• Configure voltage reference (ADCON1)

• Select A/D input channel (ADCON0)

• Select A/D conversion clock (ADCON0)

• Turn on A/D module (ADCON0)

Configure A/D interrupt (if desired):

• Clear ADIF bit

• Set ADIE bit

• SET PEIE bit

• Set GIE bit

Wait the required acquisition time.

Start conversion:

• Set GO/DONE bit (ADCON0)

Wait for A/D conversion to complete, by either:

• Polling for the GO/DONE bit to be cleared

(with interrupts disabled); OR

• Waiting for the A/D interrupt

Read A/D Result register pair

(ADRESH:ADRESL), clear bit ADIF if required.

For next conversion, go to step 1 or step 2 as

required. The A/D conversion time per bit is

defined as TAD. A minimum wait of 2 TAD is

required before the next acquisition starts.

FIGURE 12-1:

A/D BLOCK DIAGRAM

(Input Voltage)

VIN

VREF+

(Reference

Voltage)

AVDD

VCFG1:VCFG0

CHS2:CHS0

RA3/AN3/VREF+/C1OUT

RA2/AN2/CVREF/VREF-

RA1/AN1

RA0/AN0

011

010

001

000

A/D

Converter

VREF-

(Reference

Voltage)

AVSS

VCFG1:VCFG0

RB6/AN5/PGC/T1OSO/T1CKI

RB7/AN6/PGD/T1OSI

RA4/AN4/T0CKI/C2OUT

110

101

100

PIC16F87-I/ML Datasheet(PDF) 118 Page - Microchip Technology

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