Datasheet

PIC24FJ256GA110 FAMILY
DS30009905F-page 166  2007-2019 Microchip Technology Inc.
13.1.2 CASCADED (32-BIT) MODE
By default, each module operates independently with
its own 16-bit timer. To increase resolution, adjacent
even and odd modules can be configured to function as
a single 32-bit module. (For example, Modules 1 and 2
are paired, as are Modules 3 and 4, and so on.) The
odd numbered module (ICx) provides the Least Signif-
icant 16 bits of the 32-bit register pairs and the even
module (ICy) provides the Most Significant 16 bits.
Wraparounds of the ICx registers cause an increment
of their corresponding ICy registers.
Cascaded operation is configured in hardware by
setting the IC32 bits (ICxCON2[8]) for both modules.
13.2 Capture Operations
The enhanced input capture module can be configured
to capture timer values and generate interrupts on
rising edges on ICx, or all transitions on ICx. Captures
can be configured to occur on all rising edges or just
some (every 4th or 16th). Interrupts can be
independently configured to generate on each event or
a subset of events.
To set up the module for capture operations:
1. Configure the ICx input for one of the available
Peripheral Pin Select pins.
2. If Synchronous mode is to be used, disable the
sync source before proceeding.
3. Make sure that any previous data have been
removed from the FIFO by reading ICxBUF until
the ICBNE bit (ICxCON1[3]) is cleared.
4. Set the SYNCSELx bits (ICxCON2[4:0]) to the
desired sync/trigger source.
5. Set the ICTSELx bits (ICxCON1[12:10]) for the
desired clock source.
6. Set the ICIx bits (ICxCON1[6:5]) to the desired
interrupt frequency
7. Select Synchronous or Trigger mode operation:
a) Check that the SYNCSELx bits are not set
to ‘00000’.
b) For Synchronous mode, clear the ICTRIG
bit (ICxCON2[7]).
c) For Trigger mode, set ICTRIG and clear the
TRIGSTAT bit (ICxCON2[6]).
8. Set the ICMx bits (ICxCON1[2:0]) to the desired
operational mode.
9. Enable the selected trigger/sync source.
For 32-bit cascaded operations, the setup procedure is
slightly different:
1. Set the IC32 bits for both modules (ICyCON2[8]
and (ICxCON2[8]), enabling the even numbered
module first. This ensures the modules will start
functioning in unison.
2. Set the ICTSELx and SYNCSELx bits for both
modules to select the same sync/trigger and
time base source. Set the even module first,
then the odd module. Both modules must use
the same ICTSELx and SYNCSELx settings.
3. Clear the ICTRIG bit of the even module
(ICyCON2[7]); this forces the module to run in
Synchronous mode with the odd module,
regardless of its trigger setting.
4. Use the odd module’s ICIx bits (ICxCON1[6:5])
to the desired interrupt frequency.
5. Use the ICTRIG bit of the odd module
(ICxCON2[7]) to configure Trigger or
Synchronous mode operation.
6. Use the ICMx bits of the odd module
(ICxCON1[2:0]) to set the desired capture
mode.
The module is ready to capture events when the time
base and the trigger/sync source are enabled. When
the ICBNE bit (ICxCON1[3]) becomes set, at least one
capture value is available in the FIFO. Read input
capture values from the FIFO until the ICBNE clears
to ‘0’.
For 32-bit operation, read both the ICxBUF and
ICyBUF for the full 32-bit timer value (ICxBUF for the
lsw, ICyBUF for the msw). At least one capture value is
available in the FIFO buffer when the odd module’s
ICBNE bit (ICxCON1[3]) becomes set. Continue to
read the buffer registers until ICBNE is cleared
(perform automatically by hardware).
Note: For Synchronous mode operation, enable
the sync source as the last step. Both
input capture modules are held in Reset
until the sync source is enabled.