PIC18F4321 Datasheet, PDF (232/396 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

PIC18F4321 FAMILY
The analog reference voltage is software selectable to
either the device’s positive and negative supply voltage
(VDD and VSS), or the voltage level on the RA3/AN3/
VREF+ 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
complete, the result is loaded into the
ADRESH:ADRESL register pair, 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
CHS3:CHS0
1100
1011
1010
1001
1000
0111
0110
0101
10-Bit
Converter
A/D
VAIN
(Input Voltage)
0100
0011
0010
Reference
Voltage
VCFG1:VCFG0
VREF+
VREF-
VDD
X0
X1
1X
0X
VSS
0001
0000
AN12
AN11
AN10
AN9
AN8
AN7⁽¹⁾
AN6⁽¹⁾
AN5⁽¹⁾
AN4
AN3
AN2
AN1
AN0
Note 1: Channels AN5 through AN7 are not available on 28-pin devices.
2: I/O pins have diode protection to VDD and VSS.
DS39689E-page 230
Preliminary
© 2007 Microchip Technology Inc.