PIC17C7XX_13 Datasheet, PDF (188/306 Pages) Microchip Technology – High-Performance 8-bit CMOS EPROM Microcontrollers with 10-bit A/D

PIC17C7XX
16.4.1 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 16-6 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.
16.5 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
(ADCS1:ADCS0 = 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 16-6:
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
(ADCS1:ADCS0 = 11). To allow the con-
version to occur during SLEEP, ensure the
SLEEP instruction immediately follows the
instruction that sets the GO/DONE bit.
16.6 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.
10-Bit Result
ADFM = 1
ADFM = 0
7
2107
0
0000 00
RESULT
ADRESH
ADRESL
10-bits
Right Justified
7
0765
0
RESULT
0000 00
ADRESH
ADRESL
10-bits
Left Justified
DS30289C-page 188
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