PIC18F6585/8585/6680/8680
15.2.3
SOFTWARE INTERRUPT
15.2.5
CAN MESSAGE TIME-STAMP
When the Capture mode is changed, a false capture
interrupt may be generated. The user should keep bit
CCPxIE (PIE registers) clear to avoid false interrupts
and should clear the flag bit, CCPxIF, following any
such change in operating mode.
The CAN capture event occurs when a message is
received in any of the receive buffers. When config-
ured, the CAN module provides the trigger to the CCP1
module to cause a capture event. This feature is
provided to time-stamp the received CAN messages.
This feature is enabled by setting the CANCAP bit of
the CAN I/O Control register (CIOCON<4>). The
message receive signal from the CAN module then
takes the place of the events on RC2/CCP1.
15.2.4
CCP PRESCALER
There are four prescaler settings specified by bits
CCPxM3:CCPxM0. Whenever the CCPx module is
turned off, or the CCPx module is not in Capture mode,
the prescaler counter is cleared. This means that any
Reset will clear the prescaler counter.
EXAMPLE 15-1:
CHANGING BETWEEN
CAPTURE PRESCALERS
Switching from one capture prescaler to another may
generate an interrupt. The prescaler counter will not be
cleared; therefore, the first capture may be from a
non-zero prescaler. Example 15-1 shows the
recommended method for switching between capture
prescalers. This example also clears the prescaler
counter and will not generate the “false” interrupt.
CLRF
MOVLW
CCP1CON
NEW_CAPT_PS
; Turn CCP module off
; Load WREG with the
; new prescaler mode
; value and CCP ON
; Load CCP1CON with
; this value
MOVWF
CCP1CON
FIGURE 15-1:
CAPTURE MODE OPERATION BLOCK DIAGRAM
TMR3H
TMR3L
CCPR1L
TMR1L
Set Flag bit CCP1IF
T3CCP2
T3CCP2
TMR3
Enable
Prescaler
÷ 1, 4, 16
CCP1 pin
CCPR1H
TMR1
and
Edge Detect
Enable
TMR1H
CCP1CON<3:0>
Q’s
Set Flag bit CCP2IF
T3CCP1
TMR3H
TMR3L
CCPR2L
TMR1L
T3CCP2
TMR3
Enable
Prescaler
÷ 1, 4, 16
CCP2 pin
CCPR2H
TMR1
and
Edge Detect
Enable
T3CCP2
T3CCP1
TMR1H
CCP2CON<3:0>
Q’s
DS30491C-page 170
2004 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
