Microchip Technology DM164134 Data Sheet
© 2006 Microchip Technology Inc.
DS41159E-page 247
PIC18FXX8
20.4
A/D Conversions
Figure 20-4 shows the operation of the A/D converter
after the GO bit has been set. Clearing the GO/DONE
bit during a conversion will abort the current conver-
sion. The A/D Result register pair will not be updated
with the partially completed A/D conversion sample.
That is, the ADRESH:ADRESL registers will continue
to contain the value of the last completed conversion
(or the last value written to the ADRESH:ADRESL
registers). After the A/D conversion is aborted, a 2 T
after the GO bit has been set. Clearing the GO/DONE
bit during a conversion will abort the current conver-
sion. The A/D Result register pair will not be updated
with the partially completed A/D conversion sample.
That is, the ADRESH:ADRESL registers will continue
to contain the value of the last completed conversion
(or the last value written to the ADRESH:ADRESL
registers). After the A/D conversion is aborted, a 2 T
AD
wait is required before the next acquisition is started.
After this 2 T
After this 2 T
AD
wait, acquisition on the selected
channel is automatically started.
20.4.1
A/D RESULT REGISTERS
The ADRESH:ADRESL register pair is the location
where the 10-bit A/D result is loaded at the completion
of the A/D conversion. This register pair is 16 bits wide.
The A/D module gives the flexibility to left or right justify
the 10-bit result in the 16-bit result register. The A/D
Format Select bit (ADFM) controls this justification.
Figure 20-3 shows the operation of the A/D result justi-
fication. The extra bits are loaded with ‘0’s. When an
A/D result will not overwrite these locations (A/D
disable), these registers may be used as two general
purpose 8-bit registers.
where the 10-bit A/D result is loaded at the completion
of the A/D conversion. This register pair is 16 bits wide.
The A/D module gives the flexibility to left or right justify
the 10-bit result in the 16-bit result register. The A/D
Format Select bit (ADFM) controls this justification.
Figure 20-3 shows the operation of the A/D result justi-
fication. The extra bits are loaded with ‘0’s. When an
A/D result will not overwrite these locations (A/D
disable), these registers may be used as two general
purpose 8-bit registers.
FIGURE 20-3:
A/D RESULT JUSTIFICATION
Note:
The GO/DONE bit should NOT be set in
the same instruction that turns on the A/D.
the same instruction that turns on the A/D.
10-bit Result
ADRESH
ADRESL
0000 00
ADFM = 0
0
2 1 0 7
7
10-bit Result
ADRESH
ADRESL
10-bit Result
0000 00
7
0 7 6 5
0
ADFM = 1
Right Justified
Left Justified