PIC18F87J10 Datasheet, PDF (252/394 Pages) Microchip Technology – 64/80-Pin High-Performance, 1-Mbit Flash Microcontrollers with nanoWatt Technology

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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
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.
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
register pair, the GO/DONE bit (ADCON0<1>) is
cleared and A/D Interrupt Flag bit ADIF is set.
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. The value in the
ADRESH:ADRESL register pair is not modified for a
Power-on Reset. These registers will contain unknown
data after a Power-on Reset.
The block diagram of the A/D module is shown in
Figure 20-1.
FIGURE 20-1:
A/D BLOCK DIAGRAM
CHS3:CHS0
10-bit
Converter
A/D
Reference
Voltage
VAIN
(Input Voltage)
VCFG1:VCFG0
VREF+
VREF-
VDD
1111
1110
1101
1100
1011
1010
1001
1000
0111
0110
0100
0011
0010
0001
0000
AN15⁽¹⁾
AN14⁽¹⁾
AN13⁽¹⁾
AN12⁽¹⁾
AN11
AN10
AN9
AN8
AN7
AN6
AN4
AN3
AN2
AN1
AN0
VSS
Note 1: Channels AN15 through AN12 are not available on 64-pin devices.
2: I/O pins have diode protection to VDD and VSS.
DS39663A-page 250
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 2005 Microchip Technology Inc.