
PIC18F6585/8585/6680/8680
DS30491C-page 252
2004 Microchip Technology Inc.
The analog reference voltage is software selectable to
either the device’s positive and negative supply voltage
(AVDD and AVSS) or the voltage level on the RA3/AN3/
VREF+ and RA2/AN2/VREF- pins.
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 output of the sample and hold is the input into the
converter which generates the result via successive
approximation.
A device Reset forces all registers to their Reset state.
This forces the A/D module to be turned off and any
conversion in progress is aborted.
Each port pin associated with the A/D converter can be
configured as an analog input or as a digital I/O. The
ADRESH and ADRESL registers contain the result of
the A/D conversion. When the A/D conversion is com-
plete, the result is loaded into the ADRESH/ADRESL
registers, the GO/DONE bit (ADCON0 register) is
cleared and A/D interrupt flag bit ADIF is set. The block
FIGURE 19-1:
A/D BLOCK DIAGRAM
(Input Voltage)
VAIN
VREF+
Reference
Voltage
VDD
VCFG1:VCFG0
CHS3:CHS0
AN7
AN6
AN5
AN4
AN3
AN2
AN1
AN0
0111
0110
0101
0100
0011
0010
0001
0000
10-bit
Converter
VREF-
VSS
A/D
AN15(1)
AN14(1)
AN13(1)
AN12(1)
AN11
AN10
AN9
AN8
1111
1110
1101
1100
1011
1010
1001
1000
Note
1:
Channels AN15 through AN12 are not available on the PIC18F6X8X.
2: I/O pins have diode protection to VDD and VSS.