AT89C51AC3-RDTIM datasheet(96/143 Pages) ATMEL

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AT89C51AC3

4383B–8051–01/05

Each module in the PCA has a special function register associated with it (CCAPM0 for

module 0 ...). The CCAPM0:4 registers contain the bits that control the mode that each

module will operate in.

•

The ECCF bit enables the CCF flag in the CCON register to generate an interrupt

when a match or compare occurs in the associated module.

•

The PWM bit enables the pulse width modulation mode.

•

The TOG bit when set causes the CEX output associated with the module to toggle

when there is a match between the PCA counter and the module’s capture/compare

•

The match bit MAT when set will cause the CCFn bit in the CCON register to be set

when there is a match between the PCA counter and the module’s capture/compare

•

The two bits CAPN and CAPP in CCAPMn register determine the edge that a

capture input will be active on. The CAPN bit enables the negative edge, and the

CAPP bit enables the positive edge. If both bits are set both edges will be enabled.

•

The bit ECOM in CCAPM register when set enables the comparator function.

PCA Interrupt

Figure 54. PCA Interrupt System

PCA Capture Mode

To use one of the PCA modules in 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 reg-

isters (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.

CCON

CCF4 CCF3 CCF2 CCF1 CCF0

Module 4

Module 3

Module 2

Module 1

Module 0

PCA Timer/Counter

ECCFn

CCAPMn.0

To Interrupt

IEN0.7

IEN0.6

ECF

CMOD.0

AT89C51AC3-RDTIM 数据表(PDF) 96 Page - ATMEL Corporation

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