AT89C51RB2-RLTCM View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT89C51RB2-RLTCM

8-bit Microcontroller with 16K/32K Bytes Flash

Atmel Corporation 

16-bit Software Timer/

Compare Mode

The PCA Modules can be used as software timers by setting both the ECOM and MAT

bits in the Modules CCAPMn register. The PCA timer will be compared to the Module's

capture registers and when a match occurs, an interrupt will occur if the CCFn (CCON

SFR) and the ECCFn (CCAPMn SFR) bits for the Module are both set (see Figure 14).

Figure 14. PCA Compare Mode and PCA Watchdog Timer

Write to

CCAPnL Reset

Write to

CCAPnH

1

0

Enable

CF CR

CCAPnH

CCAPnL

16 bit Comparator

CCON

CCF4 CCF3 CCF2 CCF1 CCF0 0xD8

PCA IT

Match

CH

CL

PCA Counter/Timer

RESET(1)

CCAPMn, n = 0 to 4

ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn

0xDA to 0xDE

CIDL WDTE

CPS1 CPS0 ECF CMOD

0xD9

Note: 1. Only for Module 4

Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value,

otherwise an unwanted match could occur. Writing to CCAPnH will set the ECOM bit.

Once ECOM set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t

occur while modifying the compare value. Writing to CCAPnH will set ECOM. For this

reason, user software should write CCAPnL first, and then CCAPnH. Of course, the

ECOM bit can still be controlled by accessing to CCAPMn register.

40 AT89C51RB2/RC2

4180E–8051–10/06

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