Rainbow Electronics AT89C5131 - Manual (Page 76)

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AT89C5131
4136A–USB–03/03
Table 59. CL Register
CL - PCA Counter Register Low (0E9h)
Reset Value = 0000 0000b
Not bit addressable
PCA Capture Mode 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
(see Figure 30).
Figure 30. PCA Capture Mode
16-bit Software
Timer/Compare 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 (see Figure 31).
7 6 5 4 3 2 1 0
- - - - - - - -
Bit
Number
Bit
Mnemonic Description
7 - 0 -
PCA Counter
CL Value
CF CR
CCON
0xD8
CH CL
CCAPnH CCAPnL
CCF4 CCF3 CCF2 CCF1 CCF0
PCA IT
PCA Counter/Timer
ECOMn CCAPMn, n = 0 to 4
0xDA to 0xDE CAPNn MATn TOGn PWMn ECCFn CAPPn
Cex.n
Capture