Datasheet

PIC18F2331/2431/4331/4431
DS39616D-page 160  2010 Microchip Technology Inc.
17.1.8 SPECIAL EVENT TRIGGER
(CAP1 ONLY)
The Special Event Trigger mode of IC1
(CAP1M<3:0> = 1110 or 1111) enables the Special
Event Trigger signal. The trigger signal can be used as
the Special Event Trigger Reset input to TMR5,
resetting the timer when the specific event happens on
IC1. The events are summarized in Table 17-2.
TABLE 17-2: SPECIAL EVENT TRIGGER
17.1.9 OPERATING MODES SUMMARY
Table 17-3 shows a summary of the input capture
configuration when used in conjunction with the TMR5
timer resource.
17.1.10 OTHER OPERATING MODES
Although the IC and QEI submodules are mutually
exclusive, the IC can be reconfigured to work with the
QEI module to perform specific functions. In effect, the
QEI “borrows” hardware from the IC to perform these
operations.
For velocity measurement, the QEI uses dedicated
hardware in channel IC1. The CAP1BUF registers are
remapped, becoming the VELR registers. Its operation
and use are described in Section 17.2.6 “Velocity
Measurement”.
While in QEI mode, the CAP2BUF and CAP3BUF reg-
isters of channel IC2 and IC3 are used for position
determination. They are remapped as the POSCNT
and MAXCNT Buffer registers, respectively.
TABLE 17-3: INPUT CAPTURE TIME BASE RESET SUMMARY
CAP1M<3:0> Description
1110 The trigger occurs on every falling
edge on the CAP1 input.
1111 The trigger occurs on every rising
edge on the CAP1 input.
Pin CAPxM Mode Timer
Reset Timer
on Capture
Description
CAP1 0001-0100 Edge Capture TMR5 optional
(1)
Simple Edge Capture mode (includes a
selectable prescaler).
0101 Period Measurement TMR5 optional
(1)
Captures Timer5 on period boundaries.
0110-0111 Pulse-Width
Measurement
TMR5 always Captures Timer5 on pulse boundaries.
1000 Input Capture on State
Change
TMR5 optional
(1)
Captures Timer5 on state change.
1110-1111 Special Event Trigger
(rising or falling edge)
TMR5 optional
(2)
Used as a Special Event Trigger to be
used with the Timer5 or other peripheral
modules.
CAP2 0001-0100 Edge Capture TMR5 optional
(1)
Simple Edge Capture mode (includes a
selectable prescaler).
0101 Period Measurement TMR5 optional
(1)
Captures Timer5 on period boundaries.
0110-0111 Pulse-Width
Measurement
TMR5 always Captures Timer5 on pulse boundaries.
1000 Input Capture on State
Change
TMR5 optional
(1)
Captures Timer5 on state change.
CAP3 0001-0100 Edge Capture TMR5 optional
(1)
Simple Edge Capture mode (includes a
selectable prescaler).
0101 Period Measurement TMR5 optional
(1)
Captures Timer5 on period boundaries.
0110-0111 Pulse-Width
Measurement
TMR5 always Captures Timer5 on pulse boundaries.
1000 Input Capture on State
Change
TMR5 optional
(1)
Captures Timer5 on state change.
Note 1: Timer5 may be reset on capture events only when CAPxREN = 1.
2: Trigger mode will not reset Timer5 unless RESEN
= 0 in the T5CON register.