PIC18F1230 MICROCHIP [Microchip Technology], PIC18F1230 Datasheet - Page 173

• Manufacturer Part Number: PIC18F1230
• Description: 18/20/28-Pin, Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D
• Manufacturer: MICROCHIP [Microchip Technology]

15.7
Figure 15-4 shows the operation of the A/D converter
after the GO/DONE bit has been set and the
ACQT2:ACQT0 bits are cleared. A conversion is
started after the following instruction to allow entry into
Sleep mode before the conversion begins.
Figure 15-5 shows the operation of the A/D converter
after the GO/DONE bit has been set, the ACQT2:ACQT0
bits are set to ‘010’ and a 4 T
selected before the conversion starts.
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
ADRESH:ADRESL registers will continue to contain the
value of the last completed conversion (or the last value
written to the ADRESH:ADRESL registers).
FIGURE 15-4:
FIGURE 15-5:
© 2006 Microchip Technology Inc.
(Holding capacitor continues
acquiring input)
Set GO/DONE bit
1
Set GO/DONE bit
T
CY
A/D Conversions
Holding capacitor is disconnected from analog input (typically 100 ns)
T
ACQT
– T
Acquisition
Automatic
2
AD
Time
sample.
Conversion starts
Cycles
T
AD
3
1 T
A/D CONVERSION T
A/D CONVERSION T
AD
b9
This
4
2 T
Conversion starts
(Holding capacitor is disconnected)
AD
b8
AD
1
means
3 T
acquisition time is
AD
b7
b9
2
4 T
that
Advance Information
AD
b6
On the following cycle:
ADRESH:ADRESL are loaded, GO/DONE bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.
b8
3
AD
AD
5 T
On the following cycle:
ADRESH:ADRESL are loaded, GO/DONE bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.
CYCLES (ACQT<2:0> = 000, T
CYCLES (ACQT<2:0> = 010, T
the
AD
b5
b7
4
6 T
AD
b4
T
b6
5
AD
7 T
Cycles
After the A/D conversion is completed or aborted, a
2 T
started. After this wait, acquisition on the selected
channel is automatically started.
15.8
The discharge phase is used to initialize the value of
the capacitor array. The array is discharged before
every sample. This feature helps to optimize the unity-
gain amplifier, as the circuit always needs to charge the
capacitor array, rather than charge/discharge based on
previous measure values.
AD
b3
Note:
b5
AD
6
8
wait is required before the next acquisition can be
T
AD
b2
Discharge
b4
PIC18F1230/1330
7
9 T
The GO/DONE bit should NOT be set in
the same instruction that turns on the A/D.
AD
b1
b3
8
10
T
AD
b0
ACQ
ACQ
b2
9
11
T
= 0)
= 4 T
AD
Discharge
10
b1
1
AD
DS39758B-page 171
)
11
b0
T
Discharge
AD
1