Datasheet

PIC18F2585/2680/4585/4680
DS39625C-page 250 Preliminary © 2007 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/V
REF+ and RA2/AN2/VREF-/CVREF pins.
The A/D converter has a unique feature of being able
to operate while the device is in Sleep mode. To
operate 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 diagram of the A/D module is shown in
Figure 19-1.
FIGURE 19-1: A/D BLOCK DIAGRAM
(Input Voltage)
VAIN
VREF+
Reference
Voltage
AV
DD
VCFG1:VCFG0
CHS3:CHS0
AN7
(1)
AN6
(1)
AN5
(1)
AN4
AN3
AN2
AN1
AN0
0111
0110
0101
0100
0011
0010
0001
0000
10-Bit
Converter
VREF-
AVSS
A/D
AN10
AN9
AN8
1010
1001
1000
Note 1: Channels AN5 through AN7 are not available on PIC18F2X8X devices.
2: I/O pins have diode protection to V
DD and VSS.
0X
1X
X
1
X0