T89C51RD2-DDFC-L View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

T89C51RD2-DDFC-L

0 to 40 MHz Flash Programmable 8-bit Microcontroller

Atmel Corporation 

T89C51RD2

Write to

CCAPnL Reset

CF CR

Write to

CCAPnH

CCAPnH

CCAPnL

1

0

Enable

16 bit comparator

CCON

CCF4 CCF3 CCF2 CCF1 CCF0 0xD8

PCA IT

Match

CH

CL

CEXn

PCA counter/timer

CCAPMn, n = 0 to 4

ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn 0xDA to 0xDE

Figure 11. PCA High Speed Output Mode

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

match could happen.

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.

6.5.4. Pulse Width Modulator Mode

All of the PCA modules can be used as PWM outputs. Figure 12 shows the PWM function. The frequency of the

output depends on the source for the PCA timer. All of the modules will have the same frequency of output

because they all share the PCA timer. The duty cycle of each module is independently variable using the module's

capture register CCAPLn. When the value of the PCA CL SFR is less than the value in the module's CCAPLn

Rev. F - 15 February, 2001

30

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