2004 Microchip Technology Inc.
DS30491C-page 249
PIC18F6585/8585/6680/8680
19.0
10-BIT ANALOG-TO-DIGITAL
CONVERTER (A/D) MODULE
The Analog-to-Digital (A/D) converter module has 12
inputs for the PIC18F6X8X devices and 16 inputs for
the PIC18F8X8X devices. This module allows conver-
sion of an analog input signal to a corresponding 10-bit
digital number.
A new feature for the A/D converter is the addition of pro-
grammable acquisition time. This feature allows the user
to select a new channel for conversion and to set the
GO/DONE bit immediately. When the GO/DONE bit is
set,
the
selected
channel
is
sampled
for
the
programmed acquisition time before a conversion is
actually started. This removes the firmware overhead
that may have been required to allow for an acquisition
The module has five registers:
A/D Result High Register (ADRESH)
A/D Result Low Register (ADRESL)
A/D Control Register 0 (ADCON0)
A/D Control Register 1 (ADCON1)
A/D Control Register 2 (ADCON2)
The ADCON0 register, shown in
controls the operation of the A/D module. The
the functions of the port pins. The ADCON2 register,
source, programmed acquisition time and justification.
REGISTER 19-1:
ADCON0 REGISTER
U-0
R/W-0
—
CHS3
CHS2
CHS1
CHS0
GO/DONE
ADON
bit 7
bit 0
bit 7-6
Unimplemented: Read as ‘0’
bit 5-2
CHS3:CHS0: Analog Channel Select bits
0000
= Channel 0 (AN0)
0001
= Channel 1 (AN1)
0010
= Channel 2 (AN2)
0011
= Channel 3 (AN3)
0100
= Channel 4 (AN4)
0101
= Channel 5 (AN5)
0110
= Channel 6 (AN6)
0111
= Channel 7 (AN7)
1000
= Channel 8 (AN8)
1001
= Channel 9 (AN9)
1010
= Channel 10 (AN10)
1011
= Channel 11 (AN11)
1100
= Channel 12 (AN12)(1)
1101
= Channel 13 (AN13)(1)
1110
= Channel 14 (AN14)(1)
1111
= Channel 15 (AN15)(1)
bit 1
GO/DONE: A/D Conversion Status bit
When ADON = 1:
1
= A/D conversion in progress. This bit is automatically cleared when the A/D conversion is
complete.
0
= A/D Idle
bit 0
ADON: A/D On bit
1
= A/D converter module is enabled
0
= A/D converter module is disabled and consumes no current
Note 1: These channels are only available on PIC18F8X8X devices.
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