AT83C51RB2-RLTIM View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
AT83C51RB2-RLTIM Datasheet PDF : 83 Pages
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AT80C51RD2/AT83C51Rx2
Figure 12. PCA High-speed Output Mode
CF CR
Write to
CCA PnL Reset
Write to
CCA PnH
CCA PnH
CCAPnL
1
0
E na ble
16 bit comparator
CCO N
CCF4 CCF3 CCF2 CCF1 CCF0 0xD8
PCA IT
Ma tch
CH
CL
CEX n
PCA counter/timer
CCAPMn, n = 0 to 4
ECO MnCAPPn CAPNn MATn TOGn PWMn ECCFn 0xDA to 0xDE
Pulse Width Modulator
Mode
Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value,
otherwise an unwanted match could occur.
Once ECOM is 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 the CCAPMn register.
All of the PCA modules can be used as PWM outputs. Figure 13 shows the PWM func-
tion. 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 mod-
ule'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.
33
4113B–8051–03/05
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