83C51FA与83c51FB的可编程计数器阵列PCA的功能

This application note illustrates the different functions of the Programmable Counter Array (PCA) which are available on the 83C51FA and 83C51FB. Included are
cookbook samples of code in typical applications to simplify the use of the PCA. Since all the examples are written in assembly language, it is assumed the reader is
familiar with ASM51. For further information on these products or ASM51 refer to the Embedded Controller Handbook (Vol. I).
CONTENTS PAGE
PCA OVERVIEW  1
PCA TIMER/COUNTER  1
COMPARE/CAPTURE MODULES  3
CAPTURE MODE  5
Measuring Pulse Widths  5
Measuring Periods  7
Measuring Frequencies  7
Measuring Duty Cycles  9
Measuring Phase Differences  10
Reading the PCA Timer  13
COMPARE MODE  13
SOFTWARE TIMER  13
HIGH SPEED OUTPUT  15
WATCHDOG TIMER  18
PULSE WIDTH MODULATOR  19
CONCLUSION  21
APPENDICES
A. Test Routines  A-1
B. Duty Cycle Calculation  B-1
C. Special Function Registers  C-1
FIGURES PAGE
1. PCA Timer/Counter and Compare/
Capture Modules  1
2. PCA Interrupt  4
3. PCA Capture Mode  5
4. Measuring Pulse Width  5
5. Measuring Period  7
6. Measuring Frequency  7
7. Measuring Duty Cycle  9
8. Measuring Phase Differences  10
9. Software Timer Mode  13
10. High Speed Output Mode  15
11. Watchdog Timer Mode  18
12. PWM Mode  19
13. CCAPnH Varies Duty Cycle  20
LISTINGS PAGE
1. Measuring Pulse Widths  6
2. Measuring Frequencies  8
3. Measuring Duty Cycle  9
4. Measuring Phase Differences  11
5. Software Timer  14
6. High Speed Output (Without
Interrupt)  15
7. High Speed Output (With Interrupt)  16
8. High Speed Output (Single Pulse)  17
9. Watchdog Timer  19
10. PWM  21
TABLES PAGE
1. PCA Timer/Counter Inputs  2
2. CMOD Values  2
3. Compare/Capture Mode Values  3
4. PWM Frequencies  20