AT89C51RB2-3CSIM datasheet(33/127 Pages) ATMEL

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AT89C51RB2/RC2

4180C–8051–12/03

Registers

Table 22. CMOD Register

CMOD – PCA Counter Mode Register (D9h)

Reset Value = 00XX X000b

Not bit addressable

The CMOD register includes three additional bits associated with the PCA.

•

The CIDL bit which allows the PCA to stop during idle mode.

•

The WDTE bit which enables or disables the watchdog function on Module 4.

•

The ECF bit which when set causes an interrupt and the PCA overflow flag CF (in

the CCON SFR) to be set when the PCA timer overflows.

The CCON register contains the run control bit for the PCA and the flags for the PCA

timer (CF) and each Module (see Table 23).

•

Bit CR (CCON. 6) must be set by software to run the PCA. The PCA is shut off by

clearing this bit.

•

Bit CF: The CF bit (CCON. 7) is set when the PCA counter overflows and an

interrupt will be generated if the ECF bit in the CMOD register is set. The CF bit can

only be cleared by software.

•

Bits 0 through 4 are the flags for the Modules (bit 0 for Module 0, bit 1 for Module 1,

etc. ) and are set by hardware when either a match or a capture occurs. These flags

also can only be cleared by software.

CIDL

WDTE

CPS1

CPS0

ECF

Bit

Number

Bit

Mnemonic

Description

7CIDL

Counter Idle Control

Cleared to program the PCA Counter to continue functioning during idle Mode.

Set to program PCA to be gated off during idle.

6WDTE

Watchdog Timer Enable

Cleared to disable Watchdog Timer function on PCA Module 4.

Set to enable Watchdog Timer function on PCA Module 4.

Reserved

The value read from this bit is indeterminate. Do not set this bit.

Reserved

The value read from this bit is indeterminate. Do not set this bit.

Reserved

The value read from this bit is indeterminate. Do not set this bit.

CPS1

PCA Count Pulse Select

CPS1 CPS0

Selected PCA input

Internal clock F

CLK PERIPH/6

Internal clock F

LK PERIPH/2

Timer 0 Overflow

External clock at ECI/P1.2 pin (max rate = fCLK PERIPH/ 4)

CPS0

0ECF

PCA Enable Counter Overflow Interrupt

Cleared to disable CF bit in CCON to inhibit an interrupt.

Set to enable CF bit in CCON to generate an interrupt.

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