PIC18F1220_07 Datasheet, PDF (164/308 Pages) Microchip Technology – 18/20/28-Pin High-Performance, Enhanced Flash Microcontrollers with 10-bit A/D and nanoWatt Technology

PIC18F1220/1320
17.5 Operation in Low-Power Modes
The selection of the automatic acquisition time and the
A/D conversion clock is determined, in part, by the low-
power mode clock source and frequency while in a
low-power mode.
If the A/D is expected to operate while the device is
in a low-power mode, the ACQT2:ACQT0 and
ADCS2:ADCS0 bits in ADCON2 should be updated in
accordance with the low-power mode clock that will be
used. After the low-power mode is entered (either of
the Run modes), an A/D acquisition or conversion may
be started. Once an acquisition or conversion is
started, the device should continue to be clocked by the
same low-power mode clock source until the conver-
sion has been completed. If desired, the device may be
placed into the corresponding low-power (ANY)_IDLE
mode during the conversion.
If the low-power mode clock frequency is less than
1 MHz, the A/D RC clock source should be selected.
Operation in the Low-Power Sleep mode requires the
A/D RC clock to be selected. If bits, ACQT2:ACQT0, are
set to ‘000’ and a conversion is started, the conversion
will be delayed one instruction cycle to allow execution
of the SLEEP instruction and entry to Low-Power Sleep
mode. The IDLEN and SCS bits in the OSCCON register
must have already been cleared prior to starting the
conversion.
17.6 Configuring Analog Port Pins
The ADCON1, TRISA and TRISB registers all configure
the A/D port pins. The port pins needed as analog inputs
must have their corresponding TRIS bits set (input). If
the TRIS bit is cleared (output), the digital output level
(VOH or VOL) will be converted.
The A/D operation is independent of the state of the
CHS2:CHS0 bits and the TRIS bits.
Note 1: When reading the Port register, all pins
configured as analog input channels will
read as cleared (a low level). Pins con-
figured as digital inputs will convert an
analog input. Analog levels on a digitally
configured input will be accurately
converted.
2: Analog levels on any pin defined as a
digital input may cause the digital input
buffer to consume current out of the
device’s specification limits.
DS39605F-page 162
© 2007 Microchip Technology Inc.