PIC18F4539 Datasheet, PDF (185/322 Pages) Microchip Technology – Enhanced FLASH Microcontrollers with Single Phase Induction Motor Control Kernel

PIC18FXX39
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+ pin and RA2/AN2/VREF- pin.
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 is aborted.
Each port pin associated with the A/D converter can be
configured as an analog input (RA3 can also be a
voltage reference) 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 registers, the GO/DONE bit (ADCON0<2>) is
cleared, and A/D interrupt flag bit, ADIF is set. The block
diagram of the A/D module is shown in Figure 18-1.
FIGURE 18-1:
A/D BLOCK DIAGRAM
CHS<2:0>
111
110
101
100
VAIN
(Input Voltage)
011
010
10-bit
Converter
A/D
001
PCFG<3:0>
000
VDD
VREF+
Reference
Voltage
VREF-
VSS
* These channels are implemented only on the PIC18F4X39 devices.
AN7*
AN6*
AN5*
AN4
AN3
AN2
AN1
AN0
 2002 Microchip Technology Inc.
Preliminary
DS30485A-page 183