Datasheet

 2011 Microchip Technology Inc. DS39932D-page 249
PIC18F46J11 FAMILY
In addition to the expanded range of modes available
through the CCPxCON and ECCPxAS registers, the
ECCP modules have two additional registers associated
with Enhanced PWM operation and auto-shutdown
features. They are:
• ECCPxDEL (Enhanced PWM Control)
• PSTRxCON (Pulse Steering Control)
18.1 ECCP Outputs and Configuration
The Enhanced CCP module may have up to four PWM
outputs, depending on the selected operating mode.
These outputs, designated PxA through PxD, are
routed through the Peripheral Pin Select (PPS)
module. Therefore, individual functions may be
mapped to any of the remappable I/O pins, RPn. The
outputs that are active depend on the ECCP operating
mode selected. The pin assignments are summarized
in Table 18-4.
To configure the I/O pins as PWM outputs, the proper
PWM mode must be selected by setting the PxM<1:0>
and CCPxM<3:0> bits. The appropriate TRIS direction
bits for the port pins must also be set as outputs and the
output functions need to be assigned to I/O pins in the
PPS module. (For details on configuring the module,
see Section 10.7 “Peripheral Pin Select (PPS)”.)
18.1.1 ECCP MODULE AND TIMER
RESOURCES
The ECCP modules utilize Timers 1, 2, 3 or 4, depending
on the mode selected. Timer1 and Timer3 are available
to modules in Capture or Compare modes, while Timer2
and Timer4 are available for modules in PWM mode.
TABLE 18-1: ECCP MODE – TIMER
RESOURCE
The assignment of a particular timer to a module is
determined by the Timer-to-ECCP enable bits in the
TCLKCON register (Register 13-3). The interactions
between the two modules are depicted in Figure 18-1.
Capture operations are designed to be used when the
timer is configured for Synchronous Counter mode.
Capture operations may not work as expected if the
associated timer is configured for Asynchronous Counter
mode.
18.2 Capture Mode
In Capture mode, the CCPRxH:CCPRxL register pair
captures the 16-bit value of the TMR1 or TMR3
registers when an event occurs on the corresponding
ECCPx pin. An event is defined as one of the following:
• Every falling edge
• Every rising edge
•Every 4
th
rising edge
•Every 16
th
rising edge
The event is selected by the mode select bits,
CCPxM<3:0>, of the CCPxCON register. When a
capture is made, the interrupt request flag bit, CCPxIF,
is set; it must be cleared by software. If another capture
occurs before the value in register CCPRx is read, the
old captured value is overwritten by the new captured
value.
18.2.1 ECCP PIN CONFIGURATION
In Capture mode, the appropriate ECCPx pin should be
configured as an input by setting the corresponding
TRIS direction bit.
Additionally, the ECCPx input function needs to be
assigned to an I/O pin through the Peripheral Pin
Select module. For details on setting up the
remappable pins, see Section 10.7 “Peripheral Pin
Select (PPS)”.
18.2.2 TIMER1/TIMER3 MODE SELECTION
The timers that are to be used with the capture feature
(Timer1 and/or Timer3) must be running in Timer mode
or Synchronized Counter mode. In Asynchronous
Counter mode, the capture operation may not work.
The timer to be used with each ECCP module is
selected in the TCLKCON register (Register 13-3).
18.2.3 SOFTWARE INTERRUPT
When the Capture mode is changed, a false capture
interrupt may be generated. The user should keep the
CCPxIE interrupt enable bit clear to avoid false interrupts.
The interrupt flag bit, CCPxIF, should also be cleared
following any such change in operating mode.
ECCP Mode Timer Resource
Capture Timer1 or Timer3
Compare Timer1 or Timer3
PWM Timer2 or Timer4
Note: If the ECCPx pin is configured as an out-
put, a write to the port can cause a capture
condition.