AT89C5131A-RDTIL datasheet(62/184 Pages) ATMEL

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AT89C5131A-L

4338F–USB–08/07

Table 55. 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).

Bit

Number

Bit

Mnemonic

Description

7 - 0

PCA Counter

CL Value

CCON

0xD8

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

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