Microchip Technology DM164134 Data Sheet
© 2006 Microchip Technology Inc.
DS41159E-page 243
PIC18FXX8
The analog reference voltage is software selectable to
either the device’s positive and negative supply voltage
(V
either the device’s positive and negative supply voltage
(V
DD
and V
SS
) or the voltage level on the RA3/AN3/
V
REF
+ pin and RA2/AN2/V
REF
- 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.
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.
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.
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.
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 com-
plete, 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 20-1.
of the A/D conversion. When the A/D conversion is com-
plete, 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 20-1.
FIGURE 20-1:
A/D BLOCK DIAGRAM
(Input Voltage)
V
AIN
V
REF
+
Reference
voltage
V
DD
PCFG0
CHS2:CHS0
AN7
(1)
AN6
(1)
AN5
(1)
AN4
AN3
AN2
AN1
AN0
111
110
101
100
011
010
001
000
10-bit
Converter
V
REF
-
V
SS
A/D
Note 1: Channels AN5 through AN7 are not available on PIC18F2X8 devices.
2: All I/O pins have diode protection to V
DD
and V
SS
.