AT89C51AC3-RDTIM datasheet(98/140 Pages) ATMEL

98 / 140 page

AT89C51AC3

4383D–8051–02/08

High Speed Output Mode In this mode the CEX output (on port 1) associated with the PCA module will toggle

each time a match occurs between the PCA counter and the module’s capture registers.

To activate this mode the TOG, MAT, and ECOM bits in the module’s CCAPMn SFR

must be set.

Figure 57. PCA High Speed Output Mode

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 with-

out glitches. The PWM and ECOM bits in the module’s CCAPMn register must be set to

enable the PWM mode.

CCAPnH

CCAPnL

ECOMn

CCAPMn, n = 0 to 4

0xDA to 0xDE

CAPNn MATn TOGn PWMn ECCFn

CAPPn

16-bit comparator

Match

CCON

0xD8

CCF4 CCF3 CCF2

CCF1 CCF0

PCA IT

Enable

CEXn

PCA counter/timer

“1”

“0”

Write to

CCAPnL

Reset

Write to

CCAPnH

AT89C51AC3-RDTIM Datasheet(PDF) 98 Page - ATMEL Corporation

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