PIC16F74-ESLASHML datasheet(85/174 Pages) MICROCHIP

85 / 174 page

 2002 Microchip Technology Inc.

DS30325B-page 83

PIC16F7X

11.0

ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The 8-bit analog-to-digital (A/D) converter module has

five inputs for the PIC16F73/76 and eight for the

PIC16F74/77.

The A/D allows conversion of an analog input signal to

a corresponding 8-bit digital number. The output of the

sample and hold is the input into the converter, which

generates the result via successive approximation. The

analog reference voltage is software selectable to

either the device’s positive supply voltage (VDD), or the

voltage level on the RA3/AN3/VREF pin.

The A/D converter has a unique feature of being able

to operate while the device is in SLEEP mode. To oper-

ate in SLEEP, the A/D conversion clock must be

derived from the A/D’s internal RC oscillator.

The A/D module has three registers. These registers

are:

• A/D Result Register ((ADRES)

• A/D Control Register 0 (ADCON0)

• A/D Control Register 1 ((ADCON1)

The ADCON0 register, shown in Register 11-1, con-

trols the operation of the A/D module. The ADCON1

tions of the port pins. The port pins can be configured

as analog inputs (RA3 can also be a voltage reference),

or as digital I/O.

Additional information on using the A/D module can be

found in the PICmicro™ Mid-Range MCU Family Ref-

erence Manual (DS33023) and in Application Note,

AN546 (DS00546).

ADCON0 REGISTER (ADDRESS 1Fh)

R/W-0

U-0

R/W-0

ADCS1

ADCS0

CHS2

CHS1

CHS0

GO/DONE

—

ADON

bit 7

bit 0

bit 7-6

ADCS1:ADCS0: A/D Conversion Clock Select bits

= FOSC/2

= FOSC/8

= FOSC/32

= FRC (clock derived from the internal A/D module RC oscillator)

bit 5-3

CHS2:CHS0: Analog Channel Select bits

000

= Channel 0 (RA0/AN0)

001

= Channel 1 (RA1/AN1)

010

= Channel 2 (RA2/AN2)

011

= Channel 3 (RA3/AN3)

100

= Channel 4 (RA5/AN4)

101

= Channel 5 (RE0/AN5)(1)

110

= Channel 6 (RE1/AN6)(1)

111

= Channel 7 (RE2/AN7)(1)

bit 2

GO/DONE: A/D Conversion Status bit

If ADON = 1:

= A/D conversion in progress (setting this bit starts the A/D conversion)

= A/D conversion not in progress (this bit is automatically cleared by hardware when the

A/D conversion is complete)

bit 1

Unimplemented: Read as '0'

bit 0

ADON: A/D On bit

= A/D converter module is operating

= A/D converter module is shut-off and consumes no operating current

Note 1: A/D channels 5, 6 and 7 are implemented on the PIC16F74/77 only.

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR reset

’1’ = Bit is set

’0’ = Bit is cleared

x = Bit is unknown

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