AT89C51ID2-SLSIM Atmel, AT89C51ID2-SLSIM Datasheet - Page 48

• Manufacturer Part Number: AT89C51ID2-SLSIM
• Description: C51ID2 64KF TWI 32KHZ PLCC44 3-5.5V IND.
• Manufacturer: Atmel

PCA Capture Mode
Figure 16. PCA Capture Mode
16-bit Software Timer/
Compare Mode
4289C–8051–11/05
Cex.n
CF
ECOMn
CR
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 mod-
ule (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 16).
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 (See Figure 17).
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
CCAPnL
CL
AT89C51ID2
PCA IT
48