PIC18F242 datasheet(183/332 Pages) MICROCHIP

183 / 332 page

DS39564C-page 181

PIC18FXX2

17.0

COMPATIBLE 10-BIT

ANALOG-TO-DIGITAL

CONVERTER (A/D) MODULE

The Analog-to-Digital (A/D) converter module has five

inputs for the PIC18F2X2 devices and eight for the

PIC18F4X2 devices. This module has the ADCON0

and ADCON1 register definitions that are compatible

with the mid-range A/D module.

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

a corresponding 10-bit digital number.

The A/D module has four registers. These registers

are:

• A/D Result High Register (ADRESH)

• A/D Result Low Register (ADRESL)

• A/D Control Register 0 (ADCON0)

• A/D Control Register 1 (ADCON1)

The ADCON0 register, shown in Register 17-1, con-

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

functions of the port pins.

ADCON0 REGISTER

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 (ADCON0 bits in bold)

bit 5-3

CHS2:CHS0: Analog Channel Select bits

000

= channel 0, (AN0)

001

= channel 1, (AN1)

010

= channel 2, (AN2)

011

= channel 3, (AN3)

100

= channel 4, (AN4)

101

= channel 5, (AN5)

110

= channel 6, (AN6)

111

= channel 7, (AN7)

Note:

The PIC18F2X2 devices do not implement the full 8 A/D channels; the unimplemented

selections are reserved. Do not select any unimplemented channel.

bit 2

GO/DONE: A/D Conversion Status bit

When ADON = 1:

= A/D conversion in progress (setting this bit starts the A/D conversion which is automatically

cleared by hardware when the A/D conversion is complete)

= A/D conversion not in progress

bit 1

Unimplemented: Read as '0'

bit 0

ADON: A/D On bit

= A/D converter module is powered up

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

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

ADCON1

<ADCS2>

ADCON0

<ADCS1:ADCS0>

Clock Conversion

FOSC/2

FOSC/8

FOSC/32

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

FOSC/4

FOSC/16

FOSC/64

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

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