PIC16F872 Datasheet, PDF (92/160 Pages) Microchip Technology – 28-Pin, 8-Bit CMOS FLASH Microcontroller

PIC16F872
10.4.1 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 justifica-
tion. Figure 10-4 shows the operation of the A/D result
justification. 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.
10.5 A/D Operation During Sleep
The A/D module can operate during SLEEP mode. This
requires that the A/D clock source be set to RC
(ADCS<1:0> = 11). When the RC clock source is
selected, the A/D module waits one instruction cycle
before starting the conversion. This allows the SLEEP
instruction to be executed, which eliminates all digital
switching noise from the conversion. When the conver-
sion is completed, the GO/DONE bit will be cleared and
the result loaded into the ADRES register. If the A/D
interrupt is enabled, the device will wake-up from
FIGURE 10-4: A/D RESULT JUSTIFICATION
SLEEP. If the A/D interrupt is not enabled, the A/D mod-
ule will then be turned off, although the ADON bit will
remain set.
When the A/D clock source is another clock option (not
RC), a SLEEP instruction will cause the present conver-
sion to be aborted and the A/D module to be turned off,
though the ADON bit will remain set.
Turning off the A/D places the A/D module in its lowest
current consumption state.
Note:
For the A/D module to operate in SLEEP,
the A/D clock source must be set to RC
(ADCS<1:0> = 11). To allow the conver-
sion to occur during SLEEP, ensure the
SLEEP instruction immediately follows the
instruction that sets the GO/DONE bit.
10.6 Effects of a Reset
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.
The value that is in the ADRESH:ADRESL registers is
not modified for a Power-on Reset. The
ADRESH:ADRESL registers will contain unknown data
after a Power-on Reset.
ADFM = 1
10-Bit Result
ADFM = 0
7
2107
0
0000 00
ADRESH
ADRESL
10-bit Result
Right Justified
7
0765
0
0000 00
ADRESH
ADRESL
10-bit Result
Left Justified
DS30221A-page 92
Preliminary
© 1999 Microchip Technology Inc.