PIC Peripheral Interface Controllers

CCP and ECCP

programming

Amit Kulkarni

Objectives

CCP/ECCP/PWM Modules

� CCP: compare/capture module

� ECCP: Enhanced CCP

� PWM: Pulse width module

� Depending upon the family PIC18 may have

0 to 5 CCP modules.

� PWM is the feature of CCP

� CCP are enhanced in the recent years and

are termed as ECCP

Number of CCP modules

� Depends on the PIC family

� A given family member can have 2 standard CCP

modules and 1 or more ECCPs.modules and 1 or more ECCPs.

� Following table lists the various CCPs and ECCPs:

CCP programming

� PIC18 timers are used as follows:

� Usage of timers is different for different CCP

features.

� T3CON register is used to chose the timer for

CCP modes.

CCP registers

� Each CCP has three registers associated

with it.

CCPxCON: 8-bit control register� CCPxCON: 8-bit control register

� CCPRxL and CCPRxH: Can be used as

– low and high byte of 16-bit register

– 16-bit compare register

– 16-bit capture resigter

– 8-bit duty cycle register by PWM.

** but not all at the same time.

CCPxCON register

CCPxCON register contd..

CCPR1H and CCPR1L: data register

� CCP1 high and low byte registers

– low and high byte of 16-bit register

– 16-bit compare register

– 16-bit capture register

– 8-bit duty cycle register by PWM.

CCP pins: PIC18F4520 has 2 CCPs

Interaction for timer resources

� This mode can be selected using the select

bit of CCPxCON register.

This mode can cause an event out side the

Compare mode programming

� This mode can cause an event out side the

controller such as turning on the device

connected to CCP pin, or starting the ADC

conversion.

� This happens when the TMR1 or TMR3

values matches with the CCPR1H and

CCPR1L

Compare mode programming

� In Compare mode, the 16-bit CCPRx register

value is constantly compared against either

the TMR1 or TMR3 register pair value.the TMR1 or TMR3 register pair value.

� When a match occurs, the CCPx pin can be:

– driven high

– driven low

– toggled (high-to-low or low-to-high)

– remain unchanged (that is, reflects the state of

the I/O latch)

� Notice for the above first 3 options CCP pin

must be configured as an output.

Once the match is detected the CCP1IF bit of

Compare mode programming

� Once the match is detected the CCP1IF bit of

PIR1 register is set.

� T3CON register is used to select TMR1 and

TMR3.

T3CON register

T3CON register

Example

Compare mode steps for programming

Program 15-1

Capture mode programming

� In Capture mode, the CCPRxH:CCPRxL

register pair captures the 16-bit value of the

TMR1 or TMR3 registers when an eventTMR1 or TMR3 registers when an event

occurs on the corresponding CCPx pin.

� An event is defined as one of the following:

– every falling edge

– every rising edge

– every 4th rising edge

– every 16th rising edge

Capture mode programming

� The event is selected by the mode select

bits, CCPxM3:CCPxM0 (CCPxCON<3:0>).

When a capture is made, the interrupt� When a capture is made, the interrupt

request flag bit, CCPxIF, is set;

� It must be cleared in software. If another

capture occurs before the value in register

CCPRx is read, the old captured value is

overwritten by the new captured value.

PIR1 register

PIR1 register

Steps for capture mode programming

Program 15-2

Compare mode operation

PWM

� PWM: Pulse-width modulation (PWM), or pulse-

duration modulation(PDM), is a modulation

technique that conforms the width of the pulse,technique that conforms the width of the pulse,

formally the pulse duration, based on modulator

signal information.

� Its main use is to allow the control of the power

supplied to electrical devices, especially to inertial

loads such as motors.

PWM mode

� Allows us to create pulses with variable

widths.

In Pulse Width Modulation (PWM) mode, the� In Pulse Width Modulation (PWM) mode, the

CCPx pin produces up to a 10-bit resolution

PWM output.

� Since the CCP2 pin is multiplexed with a

PORTB or PORTC data latch, the

appropriate TRIS bit must be cleared to

make the CCP2 pin an output.

The period of PWM

� The CCP module uses Timer2 and its

associated registers, PR2 for PWM time

base.base.

� PR2 register is used to set the period of

PWM.

� Tosc=1/Fosc, N=pre-scaler(1,4 or 16)

The period of PWM

PWM duty cycle

� Duty cycle of PWM is the period of the pulse

for which it stays high relative to entire

period.period.

� To set the duty cycle CCP module uses 10-

bit register of DC1B9:DC1B0.

� Upper 8-bits come from CCPR1L and

remaining lower 2 bits come from CCP1CON

register.

Set-up for PWM