PIC18F2455_07 Datasheet, PDF (264/430 Pages) Microchip Technology – 28/40/44-Pin, High Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
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.
FIGURE 21-1:
A/D BLOCK DIAGRAM
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
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 21-1.
10-Bit
Converter
A/D
Reference
Voltage
CHS3:CHS0
1100
1011
1010
1001
1000
0111
0110
0101
VAIN
(Input Voltage)
0100
0011
0010
VCFG1:VCFG0
VDD⁽²⁾
X0
VREF+
X1
1X
VREF-
0X
VSS⁽²⁾
0001
0000
Note 1: Channels AN5 through AN7 are not available on 28-pin devices.
2: I/O pins have diode protection to VDD and VSS.
AN12
AN11
AN10
AN9
AN8
AN7⁽¹⁾
AN6⁽¹⁾
AN5⁽¹⁾
AN4
AN3
AN2
AN1
AN0
DS39632D-page 262
Preliminary
© 2007 Microchip Technology Inc.