Capture/Compare/PWM (CCP)/Enhanced PWM (ECCP) Peripheral

Last modified by Microchip on 2023/11/10 11:10

Contents

The CCP/ECCP is a multipurpose peripheral module inside most of the PIC® MCU devices. The module includes four unique but related peripherals:

  1. Capture mode - retrieves a timer value based on a signal event.
  2. Compare mode - constantly monitors a timer counter value and compares it to a value set in the application. Compare mode will trigger an event when the values match.
  3. Pulse Width Modulation (PWM) - produces a variable pulse width signal based on a pulse width and period value set in the application's code.
  4. Enhanced Pulse Width Modulation (EPWM) - produces a variable pulse width signal based on a pulse width and period value set in the application's code along with auto-shutdown, auto-restart, dead-band delay, and PWM steering modes. In addition, the EPWM can drive various PWM arrangements:
  • Single PWM
  • Half-Bridge PWM
  • Full-Bridge PWM, Forward Mode
  • Full-Bridge PWM, Reverse Mode
  • Single PWM with PWM Steering Mode

Capture/Compare/PWM Control Register (CCPCON)

The four modes of operation are selected and controlled by the Capture/Compare/PWM Control Register CCPCON.

CCPxCON: CCPx Control Register

R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0
PxM1PxM0DCxB1DCxB0CCPxM3CCPxM2CCPxM1CCPxM0
bit 7      bit 0

bit 3-0

CCPxM<3:0>: CCP/ECCP Mode Select bits

All Modes Off
0000 = Capture/Compare/PWM off (resets ECCPx module)

Capture Settings
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

Compare Settings
0010 = Compare mode: toggle output on match
1000 = Compare mode: initialize ECCPx pin low; set output on compare match (set CCPxIF)
1001 = Compare mode: initialize ECCPx pin high; clear output on compare match (set CCPxIF)
1010 = Compare mode: generate software interrupt only; ECCPx pin reverts to I/O state
1011 = Compare mode: Special Event Trigger

CCP Modules Only
11xx = PWM mode

ECCP Modules only
1100 = PWM mode: PxA, PxC active-high; PxB, PxD active-high
1101 = PWM mode: PxA, PxC active-high; PxB, PxD active-low
1110 = PWM mode: PxA, PxC active-low; PxB, PxD active-high
1111 = PWM mode: PxA, PxC active-low; PxB, PxD active-low

CCPxCON: CCPx Control Register

R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0
PxM1PxM0DCxB1DCxB0CCPxM3CCPxM2CCPxM1CCPxM0
bit 7      bit 0

bit 5-4

DCxB<1:0>: PWM Duty Cycle Least Significant bits

PWM Mode Only
These bits are the two LSbs of the PWM duty cycle. The eight MSbs are found in the CCPRxL register.

CCPxCON: CCPx Control Register

R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0R/W-0
PxM1PxM0DCxB1DCxB0CCPxM3CCPxM2CCPxM1CCPxM0
bit 7      bit 0

bit 7-6

PxM<1:0>: Enhanced PWM Output Configuration bits

If CCPxM<3:2> = 00, 01, 10
xx = PxA assigned as Capture/Compare input; PxB, PxC, PxD assigned as port pins

If CCPxM<3:2> = 11
00 = Single output; PxA modulated; PxB, PxC, PxD assigned as port pins
01 = Full-Bridge output forward; PxD modulated; PxA active; PxB, PxC inactive
10 = Half-Bridge output; PxA, PxB modulated with dead-band control; PxC, PxD assigned as port pins
11 = Full-Bridge output reverse; PxB modulated; PxC active; PxA, PxD inactive

Compare mode operates identically for both CCPx and ECCPx peripherals. Compare mode makes use of the 16-bit Timer1 peripheral. The 16-bit value of the combined 8-bit Compare register pair; CCPRxH:CCPRxL is constantly compared against the 16-bit value of the Timer1 register pair; TMR1H:TMR1L. When a match occurs, one of the following events can occur:

  • Toggle the CCPx output pin
  • Set the CCPx output pin
  • Clear the CCPx output pin
  • Generate a Special Event Trigger
  • Generate a Software Interrupt

The event action is based on the value of the CCPxM<3:0> control bits of the CCPxCON register. At the same time, the interrupt flag CCPxIF bit is set. All Compare modes can generate an interrupt (except for the Special Event Mode).

Back to Top