Capture Mode; Software Timer Mode - STC micro STC8A8K64D4 Series Reference Manual

STC8A8K64D4 Series Manual
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18.3.1 Capture Mode

At least one of CAPNn and CAPPn bits in CCAPMn must be set (or all of them are set) for a PCA module to
operate in capture mode. When a PCA module is operating in capture mode, the input hoppings on the external
CCP0/CCP1/CCP2 pins of the module are sampled. When a valid hopping is sampled, the PCA controller immediately
loads the counter values in the PCA counters, CH and CL, into the module's capture registers, CCAPnL and CCAPnH,
and sets the corresponding CCFn in the CCON register. If the ECCFn bit in CCAPMn is set to 1, an interrupt will be
generated. Since all PCA modules' interrupt entry addresses are shared, it is necessary to determine which module
generated an interrupt in the interrupt service routine and note that the interrupt flag bit must be cleared by software.
The structure of the PCA module working in capture mode is shown in the following figure.

18.3.2 Software Timer Mode

The PCA module can be used as a software timer by setting the ECOM and MAT bits in the CCAPMn register.
The PCA counter value in CL and CH is compared with the capture registers value in CCAPnL and CCAPnH. When
they are equal, CCFn in CCON is set and an interrupt is generated if ECCFn in CCAPMn is set to 1. CCFn flag bit
should be cleared by software.
The structure of PCA module working in software timer mode is shown in the following figure.
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CCON
CF CR
CH
CCAPnH CCAPnL
CCP0
CCP1
CCP2
CCP3
CCAPMn
- ECOMn CAPPn CAPNn MATn TOGn PWMn
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PCA capture mode
interrupt
6/7/8/10 bit PWM mode, rising and falling
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edge interrup
0 x 16 bit rising edge capture mode
0 x 16 bit falling edge capture mode
0 x 16 bit rising and falling edge capture mode
0 x 16 bit software timer mode
0 x 16 bit high speed pulse output mode
- - CF3 CF2 CF1 CF0
CL
ECCFn
0 0 0
PCA
interrupt
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