Datasheet

97
AT89C51AC3
4383D–8051–02/08
Figure 55. PCA Capture Mode
16-bit Software Timer
Mode
The PCA modules can be used as software timers by setting both the ECOM and MAT
bits in the modules CCAPMn register. The PCA timer will be compared to the module’s
capture registers and when a match occurs an interrupt will occur if the CCFn (CCON
SFR) and the ECCFn (CCAPMn SFR) bits for the module are both set.
Figure 56. PCA 16-bit Software Timer and High Speed Output Mode
CEXn
n = 0, 4
PCA Counter
CH
(8bits)
CL
(8bits)
CCAPnH
CCAPnL
CCFn
CCON
PCA
Interrupt
Request
- 0CAPPn CAPNn 000 ECCFn
7
CCAPMn Register (n = 0, 4)
0
CCAPnL
(8 bits)
CCAPnH
(8 bits)
- ECOMn0 0 MATn TOGn0 ECCFn
7 0
CCAPMn Register
(n = 0, 4)
CH
(8 bits)
CL
(8 bits)
16-Bit Comparator
Match
Enable
CCFn
CCON reg
PCA
Interrupt
Request
CEXn
Compare/Capture Module
PCA Counter
“0”
“1”
Reset
Write to
CCAPnL
Write to CCAPnH
For software Timer mode, set ECOMn and MATn.
For high speed output mode, set ECOMn, MATn and TOGn.
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