PIC18F4520ESLASHMLQTP datasheet(142/390 Pages) MICROCHIP

142 / 390 page

PIC18F2420/2520/4420/4520

DS39631A-page 140

Preliminary

 2004 Microchip Technology Inc.

15.1

CCP Module Configuration

Each Capture/Compare/PWM module is associated

with a control register (generically, CCPxCON) and a

data register (CCPRx). The data register, in turn, is

comprised of two 8-bit registers: CCPRxL (low byte)

and CCPRxH (high byte). All registers are both

readable and writable.

15.1.1

CCP MODULES AND TIMER

RESOURCES

The CCP modules utilize Timers 1, 2 or 3, depending

on the mode selected. Timer1 and Timer3 are available

to modules in Capture or Compare modes, while

Timer2 is available for modules in PWM mode.

TABLE 15-1:

CCP MODE – TIMER

RESOURCE

The assignment of a particular timer to a module is

determined by the Timer-to-CCP enable bits in the

T3CON register (Register 14-1). Both modules may be

active at any given time and may share the same timer

resource if they are configured to operate in the same

mode (Capture/Compare or PWM) at the same time. The

interactions between the two modules are summarized in

Figure 15-1 and Figure 15-2. In Timer1 in Asynchronous

Counter mode, the capture operation will not work.

15.1.2

CCP2 PIN ASSIGNMENT

The pin assignment for CCP2 (Capture input, Compare

and PWM output) can change, based on device config-

uration. The CCP2MX configuration bit determines

which pin CCP2 is multiplexed to. By default, it is

assigned to RC1 (CCP2MX = 1). If the configuration bit

is cleared, CCP2 is multiplexed with RB3.

Changing the pin assignment of CCP2 does not auto-

matically change any requirements for configuring the

port pin. Users must always verify that the appropriate

TRIS register is configured correctly for CCP2

operation, regardless of where it is located.

TABLE 15-2:

INTERACTIONS BETWEEN CCP1 AND CCP2 FOR TIMER RESOURCES

CCP/ECCP Mode

Timer Resource

Capture

Compare

PWM

Timer1 or Timer3

Timer2

CCP1 Mode CCP2 Mode

Interaction

Capture

Each module can use TMR1 or TMR3 as the time base. The time base can be different

for each CCP.

Capture

Compare

CCP2 can be configured for the Special Event Trigger to reset TMR1 or TMR3

(depending upon which time base is used). Automatic A/D conversions on trigger event

can also be done. Operation of CCP1 could be affected if it is using the same timer as a

time base.

Compare

Capture

CCP1 can be configured for the Special Event Trigger to reset TMR1 or TMR3

(depending upon which time base is used). Operation of CCP2 could be affected if it is

using the same timer as a time base.

Compare

Either module can be configured for the Special Event Trigger to reset the time base.

Automatic A/D conversions on CCP2 trigger event can be done. Conflicts may occur if

both modules are using the same time base.

Capture

PWM(1)

None

Compare

PWM(1)

None

PWM(1)

Capture

None

PWM(1)

Compare

None

PWM(1)

PWM

Both PWMs will have the same frequency and update rate (TMR2 interrupt).

Note 1:

Includes standard and enhanced PWM operation.

PIC18F4520E/MLQTP Datasheet(PDF) 142 Page - Microchip Technology

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