PIC18F2420/2520/4420/4520
The capture and compare operations described in this
chapter apply to all standard and Enhanced CCP
modules.
15.0 CAPTURE/COMPARE/PWM
(CCP) MODULES
PIC18F2420/2520/4420/4520 devices all have two
CCP (Capture/Compare/PWM) modules. Each module
contains a 16-bit register which can operate as a 16-bit
Capture register, a 16-bit Compare register or a PWM
Master/Slave Duty Cycle register.
Note: Throughout this section and Section 16.0
“Enhanced Capture/Compare/PWM (ECCP)
Module”, references to the register and bit
names for CCP modules are referred to gener-
ically by the use of ‘x’ or ‘y’ in place of the
specific module number. Thus, “CCPxCON”
might refer to the control register for CCP1,
CCP2 or ECCP1. “CCPxCON” is used
throughout these sections to refer to the mod-
ule control register, regardless of whether the
CCP module is a standard or enhanced
implementation.
In 28-pin devices, the two standard CCP modules (CCP1
and CCP2) operate as described in this chapter. In 40/
44-pin devices, CCP1 is implemented as an Enhanced
CCP module with standard Capture and Compare
modes and Enhanced PWM modes. The ECCP imple-
mentation is discussed in Section 16.0 “Enhanced
Capture/Compare/PWM (ECCP) Module”.
REGISTER 15-1: CCPxCON: CCPx CONTROL REGISTER (28-PIN DEVICES)
U-0
—
U-0
—
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
R/W-0
DCxB1
DCxB0
CCPxM3
CCPxM2
CCPxM1
CCPxM0
bit 7
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-6
bit 5-4
Unimplemented: Read as ‘0’
DCxB<1:0>: PWM Duty Cycle bit 1 and bit 0 for CCPx Module
Capture mode:
Unused.
Compare mode:
Unused.
PWM mode:
These bits are the two LSbs (bit 1 and bit 0) of the 10-bit PWM duty cycle. The eight MSbs (DCxB<9:2>)
of the duty cycle are found in CCPRxL.
bit 3-0
CCPxM<3:0>: CCPx Module Mode Select bits
0000= Capture/Compare/PWM disabled (resets CCPx module)
0001= Reserved
0010= Compare mode, toggle output on match (CCPxIF bit is set)
0011= Reserved
0100= Capture mode, every falling edge
0101= Capture mode, every rising edge
0110= Capture mode, every 4th rising edge
0111= Capture mode, every 16th rising edge
1000= Compare mode, initialize CCPx pin low; on compare match, force CCPx pin high (CCPxIF bit is set)
1001= Compare mode, initialize CCPx pin high; on compare match, force CCPx pin low (CCPxIF bit is set)
1010= Compare mode, generate software interrupt on compare match (CCPxIF bit is set, CCPx pin
reflects I/O state)
1011= Compare mode, trigger special event; reset timer; CCP2 match starts A/D conversion (CCPxIF
bit is set)
11xx= PWM mode
© 2008 Microchip Technology Inc.
DS39631E-page 139
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