Datasheet

ManualsBrandsMICROCHIP TECHNOLOGY ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller SSOP 20 8-Bit 20 MHz I/O number 17

PIC16F785/HV785

12.1.7 CONFIGURING THE A/D

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

the selected channel must be acquired before the

conversion is started. The analog input channels must

have their corresponding TRIS bits selected as inputs.

To determine sample time, see Table 19-16 and

Table 19-17. After this sample time has elapsed, the

A/D conversion can be started.

These steps should be followed for an A/D conversion:

1. Configure the A/D module:

• Configure analog/digital I/O (ANSx)

• Select A/D conversion clock in the ADCON1

• Configure voltage reference in the ADCON0

• Select A/D input channel in the ADCON0

• Select result format in the ADCON0 Register

• Turn on A/D module in the ADCON0 Register

2. Configure A/D interrupt (if desired):

• Clear ADIF bit of the PIR1 Register

• Set ADIE bit of the PIE1 Register

• Set PEIE and GIE bits of the INTCON Regis-

ter

3. Wait the required acquisition time.

4. Start conversion:

• Set GO/DONE

bit (ADCON0<1>)

5. 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

6. Read A/D Result register pair

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

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

required. The A/D conversion time per bit is

defined as T

AD. A minimum wait of 2 TAD is

required before the next acquisition starts.

EXAMPLE 12-1: A/D CONVERSION

;This code block configures the A/D

;for polling, Vdd reference, R/C clock

;and RA0 input.

;

;Conversion start and wait for complete

;polling code included.

;

BCF STATUS,RP1 ;Bank 1

BSF STATUS,RP0 ;

MOVLW B’01110000’ ;A/D RC clock

MOVWF ADCON1

BSF TRISA,0 ;Set RA0 to input

BSF ANSEL0,0 ;Set RA0 to analog

BCF STATUS,RP0 ;Bank 0

MOVLW B’10000001’ ;Right, Vdd Vref, AN0

MOVWF ADCON0

CALL SampleTime ;Wait min sample time

BSF ADCON0,GO ;Start conversion

BTFSC ADCON0,GO ;Is conversion done?

GOTO $-1 ;No, test again

MOVF ADRESH,W ;Read upper 2 bits

MOVWF RESULTHI

BSF STATUS,RP0 ;Bank 1

MOVF ADRESL,W ;Read lower 8 bits

BCF STATUS,RP0 ;Bank 0

MOVWF RESULTLO