PIC16F882/883/884/886/887
11.4.2
TIMER1 MODE SELECTION
11.4 Compare Mode
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.
In Compare mode, the 16-bit CCPRx register value is
constantly compared against the TMR1 register pair
value. When a match occurs, the CCPx module may:
• Toggle the CCPx output
• Set the CCPx output
11.4.3
SOFTWARE INTERRUPT MODE
• Clear the CCPx output
When Generate Software Interrupt mode is chosen
(CCPxM<3:0> = 1010), the CCPx module does not
assert control of the CCPx pin (see the CCP1CON
register).
• Generate a Special Event Trigger
• Generate a Software Interrupt
The action on the pin is based on the value of the
CCPxM<3:0> control bits of the CCPx1CON register.
11.4.4
SPECIAL EVENT TRIGGER
All Compare modes can generate an interrupt.
When Special Event Trigger mode is chosen
(CCPxM<3:0> = 1011), the CCPx module does the
following:
FIGURE 11-2:
COMPARE MODE
OPERATION BLOCK
DIAGRAM
• Resets Timer1
• Starts an ADC conversion if ADC is enabled
CCPxCON<3:0>
Mode Select
The CCPx module does not assert control of the CCPx
pin in this mode (see the CCPxCON register).
Set CCPxIF Interrupt Flag
The Special Event Trigger output of the CCP occurs
immediately upon a match between the TMR1H,
TMR1L register pair and the CCPRxH, CCPRxL
register pair. The TMR1H, TMR1L register pair is not
reset until the next rising edge of the Timer1 clock. This
allows the CCPRxH, CCPRxL register pair to
effectively provide a 16-bit programmable period
register for Timer1.
(PIRx)
4
CCPx
Pin
CCPRxH CCPRxL
Comparator
Q
S
R
Output
Logic
Match
TMR1H TMR1L
TRIS
Output Enable
Special Event Trigger
Note 1: The Special Event Trigger from the CCP
module does not set interrupt flag bit
TMRxIF of the PIR1 register.
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.
2: Removing the match condition by
changing the contents of the CCPRxH
and CCPRxL 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.
11.4.1
CCP PIN CONFIGURATION
The user must configure the CCPx pin as an output by
clearing the associated TRIS bit.
Note:
Clearing the CCP1CON register will force
the CCPx compare output latch to the
default low level. This is not the PORT I/O
data latch.
© 2007 Microchip Technology Inc.
Preliminary
DS41291D-page 127
MICROCHIP [ MICROCHIP ]
