PIC18F2420-ESLASHP datasheet(141/412 Pages) MICROCHIP

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DS39631E-page 139

PIC18F2420/2520/4420/4520

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.

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”

The capture and compare operations described in this

chapter apply to all standard and Enhanced CCP

modules.

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.

CCPxCON: CCPx CONTROL REGISTER (28-PIN DEVICES)

U-0

R/W-0

—

DCxB1

DCxB0

CCPxM3

CCPxM2

CCPxM1

CCPxM0

bit 7

bit 0

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

-n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

bit 7-6

Unimplemented:

Read as ‘0’

bit 5-4

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

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