Rainbow Electronics T89C5115 - Manual (Page 71)

71
T89C5115
4128A–8051–04/02
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 34. 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.
CH CL
CCAPnH CCAPnL
ECOMn
CCAPMn, n = 0 to 1
0xDA to 0xDE
CAPNn MATn TOGn PWMn ECCFn CAPPn
16 bit comparator
Match
CF CR
CCON
0xD8
CCF1 CCF0
PCA IT
Enable
CEXn
PCA counter/timer
“1” “0”
Write to
CCAPnL
Reset
Write to
CCAPnH