TS87C51RC2 데이터 시트보기 (PDF) - International Rectifier

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TS87C51RC2

High Performance 8-bit Microcontroller

International Rectifier 

Figure 6-8. PCA High Speed Output Mode

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

6.3.4

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

wise 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.

Pulse Width Modulator Mode

All of the PCA modules can be used as PWM outputs. Figure 6-9 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 SFR the output will be low,

when it is equal to or greater than the output will be high. When CL overflows from FF to 00,

CCAPLn is reloaded with the value in CCAPHn. This allows updating the PWM without glitches.

The PWM and ECOM bits in the module's CCAPMn register must be set to enable the PWM

mode.

32 AT/TS8xC51Rx2

4188E–8051–08/06

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