PIC18F2331/2431/4331/4431
The A/D channels are grouped into four sets of 2 or
3 channels. For the PIC18F2331/2431 devices, AN0
and AN4 are in Group A, AN1 is in Group B, AN2 is in
Group C and AN3 is in Group D. For the PIC18F4331/
4431 devices, AN0, AN4 and AN8 are in Group A, AN1
and AN5 are in Group B, AN2 and AN6 are in Group C
and AN3 and AN7 are in Group D. The selected chan-
nel in each group is selected by configuring the A/D
Channel Select Register, ADCHS.
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.
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
individually be configured as an analog input or digital
I/O using the ANSEL0 and ANSEL1 registers. The
ADRESH and ADRESL registers contain the value in
the result buffer pointed to by ADPNT<1:0>
(ADCON1<1:0>). The result buffer is a 4-deep circular
buffer that has a Buffer Empty status bit, BFEMT
(ADCON1<3>), and a Buffer Overflow status bit,
BFOVFL (ADCON1<2>).
The analog voltage reference is software selectable to
either the device’s positive and negative analog supply
voltage (AVDD and AVSS), or the voltage level on the
RA3/AN3/VREF+/CAP2/QEA and RA2/AN2/VREF-/
CAP1/INDX, or some combination of supply and
external sources. Register ADCON1 controls the
voltage reference settings.
FIGURE 21-1:
A/D BLOCK DIAGRAM
VCFG<1:0>
(2)
(2)
AVSS
AVDD
VREF+
VREF-
VREFH
VREFL
ADC
AN0
AN4
AN8(1)
Analog
MUX
ADRESH, ADRESL
MUX
10
AN2/VREF-
ADPNT<1:0>
AN6(1)
00
01
10
11
1
2
3
4
S/H-1
+
ACMOD<1:0>,
GxSEL<1:0>
S/H
-
4x10-Bit FIFO
AVSS
ACONV
ACSCH
ACMODx
AN1
AN5(1)
Analog
MUX
AN3/VREF+
S/H-2
+
AN7(1)
S/H
-
(2)
ACMOD<1:0>,
GxSEL<1:0>
AVSS
Seq.
Cntrl.
Note 1: AN5 through AN8 are available only on PIC18F4331/4431 devices.
2: I/O pins have diode protection to VDD and VSS.
DS39616D-page 246
2010 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
