PIC18F87K90 Datasheet, PDF (383/566 Pages) Microchip Technology – 64/80-Pin, High-Performance Microcontrollers with LCD Driver and nanoWatt XLP Technology

PIC18F87K90 FAMILY
23.7 A/D Conversions
Figure 23-6 shows the operation of the A/D Converter
after the GO/DONE bit has been set and the
ACQT<2:0> bits are cleared. A conversion is started
after the following instruction to allow entry into Sleep
mode before the conversion begins.
Figure 23-7 shows the operation of the A/D Converter
after the GO/DONE bit has been set, the ACQT<2:0>
bits set to ‘010’ and a 4 TAD acquisition time selected.
Clearing the GO/DONE bit during a conversion will
abort the current conversion. The A/D Result register
pair will NOT be updated with the partially completed
A/D conversion sample. This means 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 completed or aborted, a
2 TAD wait is required before the next acquisition can be
started. After this wait, acquisition on the selected
channel is automatically started.
Note: The GO/DONE bit should NOT be set in
the same instruction that turns on the A/D.
FIGURE 23-6:
A/D CONVERSION TAD CYCLES (ACQT<2:0> = 000, TACQ = 0)
TCY - TAD TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8 TAD9 TAD10 TAD11 TAD12 TAD13
b11 b10 b9
b8 b7 b6 b5
b4
b3 b2
b1 b0
Conversion starts
Holding capacitor is disconnected from analog input (typically 100 ns)
Set GO/DONE bit
Next Q4: ADRESH:ADRESL is loaded, GO/DONE bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.
FIGURE 23-7:
A/D CONVERSION TAD CYCLES (ACQT<2:0> = 010, TACQ = 4 TAD)
TACQT Cycles
TAD Cycles
123412345678
Automatic
Acquisition
Time
b11 b10 b9 b8 b7 b6 b5
Conversion starts
(Holding capacitor is disconnected)
9 10 11
b4 b3 b2
12 13
b1 b0
Set GO/DONE bit
(Holding capacitor continues
acquiring input)
Next Q4: ADRESH:ADRESL is loaded, GO/DONE bit is cleared,
ADIF bit is set, holding capacitor is reconnected to analog input.
 2010 Microchip Technology Inc.
Preliminary
DS39957B-page 383