Datasheet

© 2008 Microchip Technology Inc. DS41262E-page 129
PIC16F631/677/685/687/689/690
11.2 Compare Mode
In Compare mode, the 16-bit CCPR1 register value is
constantly compared against the TMR1 register pair
value. When a match occurs, the CCP module may:
• Toggle the CCP1 output
• Set the CCP1 output
• Clear the CCP1 output
• Generate a Special Event Trigger
• Generate a Software Interrupt
The action on the pin is based on the value of the
CCP1M<3:0> control bits of the CCP1CON register.
All Compare modes can generate an interrupt.
FIGURE 11-2: COMPARE MODE
OPERATION BLOCK
DIAGRAM
11.2.1 CCP1 PIN CONFIGURATION
The user must configure the CCP1 pin as an output by
clearing the associated TRIS bit.
11.2.2 TIMER1 MODE SELECTION
In Compare mode, Timer1 must be running in either
Timer mode or Synchronized Counter mode. The
compare operation may not work in Asynchronous
Counter mode.
11.2.3 SOFTWARE INTERRUPT MODE
When Generate Software Interrupt mode is chosen
(CCP1M<3:0> = 1010), the CCP module does not
assert control of the CCP1 pin (see the CCP1CON
register).
11.2.4 SPECIAL EVENT TRIGGER
When Special Event Trigger mode is chosen
(CCP1M<3:0> = 1011), the CCP module does the
following:
• Resets Timer1
• Starts an ADC conversion if ADC is enabled
The CCP module does not assert control of the CCP1
pin in this mode (see the CCP1CON register).
The Special Event Trigger output of the CCP occurs
immediately upon a match between the TMR1H,
TMR1L register pair and the CCPR1H, CCPR1L
register pair. The TMR1H, TMR1L register pair is not
reset until the next rising edge of the Timer1 clock. This
allows the CCPR1H, CCPR1L register pair to
effectively provide a 16-bit programmable period
register for Timer1.
Note: Clearing the CCP1CON register will force
the CCP1 compare output latch to the
default low level. This is not the port I/O
data latch.
CCPR1H CCPR1L
TMR1H TMR1L
Comparator
QS
R
Output
Logic
Special Event Trigger
Set CCP1IF Interrupt Flag
(PIR1)
Match
TRIS
CCP1CON<3:0>
Mode Select
Output Enable
Pin
Special Event Trigger will:
• Clear TMR1H and TMR1L registers.
• NOT set interrupt flag bit TMR1IF of the PIR1 register.
• Set the GO/DONE
bit to start the ADC conversion.
CCP1
4
Note 1: The Special Event Trigger from the CCP
module does not set interrupt flag bit
TMR1IF of the PIR1 register.
2: Removing the match condition by
changing the contents of the CCPR1H
and CCPR1L register pair, between the
clock edge that generates the Special
Event Trigger and the clock edge that
generates the Timer1 Reset, will preclude
the Reset from occurring.