at89c51rd2-smsum ATMEL Corporation, at89c51rd2-smsum Datasheet - Page 43

• Manufacturer Part Number: at89c51rd2-smsum
• Description: 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

13.1
Figure 13-3. PCA Capture Mode
13.2
4235J–8051–01/08
PCA Capture Mode
16-bit Software Timer/ Compare Mode
Cex.n
To use one of the PCA modules in the capture mode either one or both of the CCAPM bits
CAPN and CAPP for that module must be set. The external CEX input for the module (on port 1)
is sampled for a transition. When a valid transition occurs the PCA hardware loads the value of
the PCA counter registers (CH and CL) into the module's capture registers (CCAPnL and
CCAPnH). If the CCFn bit for the module in the CCON SFR and the ECCFn bit in the CCAPMn
SFR are set then an interrupt will be generated (Refer to Figure 13-3).
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 regis-
ters 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 (See Figure 13-4).
CF
ECOMn
CR
CAPPn
CAPNn MATn TOGn PWMn ECCFn
CCF4 CCF3 CCF2 CCF1 CCF0
Capture
CCAPMn, n= 0 to 4
0xDA to 0xDE
CCON
0xD8
CCAPnH
PCA Counter/Timer
CH
AT89C51RD2/ED2
CCAPnL
CL
PCA IT
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