Datasheet
© 2006 Microchip Technology Inc. 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
register, shown in Register 17-2, configures the
functions of the port pins.
REGISTER 17-1: ADCON0 REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 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:
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)
0 = A/D conversion not in progress
bit 1 Unimplemented: Read as '0'
bit 0 ADON: A/D On bit
1 = A/D converter module is powered up
0 = 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
0 00 F
OSC/2
0 01 F
OSC/8
0 10 F
OSC/32
0 11 F
RC (clock derived from the internal A/D RC oscillator)
1 00 F
OSC/4
1 01 F
OSC/16
1 10 F
OSC/64
1 11 F
RC (clock derived from the internal A/D RC oscillator)