Rainbow-electronics T89C51CC02 Manual de usuario descargar pdf (Pagina 108)

108 Rev.A - May 17, 2001

Preliminary

T89C51CC02

16.6. Pulse Width Modulator Mode

All the PCA modules can be used as PWM outputs. The output frequency depends on the source for the PCA

timer. All the modules will have the same output frequency 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 it, the output will be high. When CL overflows from FF to 00, CCAPLn is reloaded with the value

in CCAPHn. the allows the PWM to be updated without glitches. The PWM and ECOM bits in the module’s

CCAPMn register must be set to enable the PWM mode.

Figure 109. PCA PWM Mode

CL rolls over from FFh TO 00h

loads CCAPnH contents into

CCAPnL

CCAPxL

CCAPn

8-Bit

Comparator

CL (8 bits)

“0

“1”

CL < CCAPnL

CL >= CCAPnL

CEX

- ECOMn0 00 0PWMn0

CCAPMn Register

1 2 ... 103 104 105 106 107 108 109 110 111 112 113 ... 136 137

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Rainbow-electronics T89C51CC02 Manual de usuario Pagina 108