PIC18F2420/2520/4420/4520
The assignment of a particular timer to a module is
15.1 CCP Module Configuration
determined by the Timer to CCP enable bits in the
T3CON register (Register 14-1). Both modules may be
active at any given time and may share the same timer
resource if they are configured to operate in the same
mode (Capture/Compare or PWM) at the same time. The
interactions between the two modules are summarized in
Figure 15-1 and Figure 15-2. In Timer1 in Asynchronous
Counter mode, the capture operation will not work.
Each Capture/Compare/PWM module is associated
with a control register (generically, CCPxCON) and a
data register (CCPRx). The data register, in turn, is
comprised of two 8-bit registers: CCPRxL (low byte)
and CCPRxH (high byte). All registers are both
readable and writable.
15.1.1
CCP MODULES AND TIMER
RESOURCES
15.1.2
CCP2 PIN ASSIGNMENT
The CCP modules utilize Timers 1, 2 or 3, depending
on the mode selected. Timer1 and Timer3 are available
to modules in Capture or Compare modes, while
Timer2 is available for modules in PWM mode.
The pin assignment for CCP2 (Capture input, Compare
and PWM output) can change, based on device config-
uration. The CCP2MX Configuration bit determines
which pin CCP2 is multiplexed to. By default, it is
assigned to RC1 (CCP2MX = 1). If the Configuration bit
is cleared, CCP2 is multiplexed with RB3.
TABLE 15-1: CCP MODE – TIMER
RESOURCE
Changing the pin assignment of CCP2 does not auto-
matically change any requirements for configuring the
port pin. Users must always verify that the appropriate
TRIS register is configured correctly for CCP2
operation, regardless of where it is located.
CCP/ECCP Mode
Timer Resource
Capture
Compare
PWM
Timer1 or Timer3
Timer1 or Timer3
Timer2
TABLE 15-2: INTERACTIONS BETWEEN CCP1 AND CCP2 FOR TIMER RESOURCES
CCP1 Mode CCP2 Mode
Interaction
Capture
Capture
Each module can use TMR1 or TMR3 as the time base. The time base can be different
for each CCP.
Capture
Compare CCP2 can be configured for the Special Event Trigger to reset TMR1 or TMR3
(depending upon which time base is used). Automatic A/D conversions on trigger event
can also be done. Operation of CCP1 could be affected if it is using the same timer as a
time base.
Compare
Compare
Capture
CCP1 can be configured for the Special Event Trigger to reset TMR1 or TMR3
(depending upon which time base is used). Operation of CCP2 could be affected if it is
using the same timer as a time base.
Compare Either module can be configured for the Special Event Trigger to reset the time base.
Automatic A/D conversions on CCP2 trigger event can be done. Conflicts may occur if
both modules are using the same time base.
Capture
Compare
PWM(1)
PWM(1)
PWM(1)
PWM(1)
PWM(1)
Capture
None
None
None
Compare None
PWM(1)
Both PWMs will have the same frequency and update rate (TMR2 interrupt).
Note 1: Includes standard and Enhanced PWM operation.
DS39631E-page 140
© 2008 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
