PIC18F2455_07 Datasheet, PDF (146/430 Pages) Microchip Technology – 28/40/44-Pin, High Performance, Enhanced Flash, USB Microcontrollers with nanoWatt Technology

PIC18F2455/2550/4455/4550
15.3 Compare Mode
In Compare mode, the 16-bit CCPRx register value is
constantly compared against either the TMR1 or TMR3
register pair value. When a match occurs, the CCPx pin
can be:
• driven high
• driven low
• toggled (high-to-low or low-to-high)
• remain unchanged (that is, reflects the state of the
I/O latch)
The action on the pin is based on the value of the mode
select bits (CCPxM3:CCPxM0). At the same time, the
interrupt flag bit, CCPxIF, is set.
15.3.1 CCP PIN CONFIGURATION
The user must configure the CCPx pin as an output by
clearing the appropriate TRIS bit.
Note:
Clearing the CCP2CON register will force
the RB3 or RC1 compare output latch
(depending on device configuration) to the
default low level. This is not the PORTB or
PORTC I/O data latch.
15.3.2 TIMER1/TIMER3 MODE SELECTION
Timer1 and/or Timer3 must be running in Timer mode,
or Synchronized Counter mode, if the CCP module is
using the compare feature. In Asynchronous Counter
mode, the compare operation may not work.
15.3.3 SOFTWARE INTERRUPT MODE
When the Generate Software Interrupt mode is chosen
(CCPxM3:CCPxM0 = 1010), the corresponding CCPx
pin is not affected. Only a CCP interrupt is generated,
if enabled, and the CCPxIE bit is set.
15.3.4 SPECIAL EVENT TRIGGER
Both CCP modules are equipped with a Special Event
Trigger. This is an internal hardware signal generated
in Compare mode to trigger actions by other modules.
The Special Event Trigger is enabled by selecting
the Compare Special Event Trigger mode
(CCPxM3:CCPxM0 = 1011).
For either CCP module, the Special Event Trigger resets
the Timer register pair for whichever timer resource is
currently assigned as the module’s time base. This
allows the CCPRx registers to serve as a programmable
period register for either timer.
The Special Event Trigger for CCP2 can also start an
A/D conversion. In order to do this, the A/D converter
must already be enabled.
FIGURE 15-2:
0
1
COMPARE MODE OPERATION BLOCK DIAGRAM
CCPR1H CCPR1L
Set CCP1IF
Comparator
Compare
Match
TMR1H TMR1L
0
Special Event Trigger
(Timer1/Timer3 Reset)
Output
Logic
4
CCP1CON<3:0>
SQ
R
CCP1 pin
TRIS
Output Enable
TMR3H TMR3L
T3CCP1
1
Special Event Trigger
(Timer1/Timer3 Reset, A/D Trigger)
T3CCP2
Set CCP2IF
Comparator
Compare
Match
Output
Logic
SQ
R
CCPR2H CCPR2L
4
CCP2CON<3:0>
CCP2 pin
TRIS
Output Enable
DS39632D-page 144
Preliminary
© 2007 Microchip Technology Inc.