TS87C51RD2 ATMEL Corporation, TS87C51RD2 Datasheet - Page 24

• Manufacturer Part Number: TS87C51RD2
• Description: (TS8xC51Rx2) High Performance 8-bit Microcontroller
• Manufacturer: ATMEL Corporation

6.3
24
Programmable Counter Array PCA
AT/TS8xC51Rx2
The PCA provides more timing capabilities with less CPU intervention than the standard
timer/counters. Its advantages include reduced software overhead and improved accuracy. The
PCA consists of a dedicated timer/counter which serves as the time base for an array of five
compare/capture modules. Its clock input can be programmed to count any one of the following
signals:
Each compare/capture modules can be programmed in any one of the following modes:
Module 4 can also be programmed as a watchdog timer (See Section "PCA Watchdog Timer",
page 33).
When the compare/capture modules are programmed in the capture mode, software timer, or
high speed output mode, an interrupt can be generated when the module executes its function.
All five modules plus the PCA timer overflow share one interrupt vector.
The PCA timer/counter and compare/capture modules share Port 1 for external I/O. These pins
are listed below. If the port is not used for the PCA, it can still be used for standard I/O.
The PCA timer is a common time base for all five modules (See Figure 6-4). The timer count
source is determined from the CPS1 and CPS0 bits in the CMOD SFR (See Table 6-4) and can
be programmed to run at:
PCA component
16-bit Counter
16-bit Module 0
16-bit Module 1
16-bit Module 2
16-bit Module 3
16-bit Module 4
• Oscillator frequency
• Oscillator frequency
• Timer 0 overflow
• External input on ECI (P1.2)
• rising and/or falling edge capture,
• software timer,
• high-speed output, or
• pulse width modulator.
• 1/12 the oscillator frequency. (Or 1/6 in X2 Mode)
• 1/4 the oscillator frequency. (Or 1/2 in X2 Mode)
• The Timer 0 overflow
• The input on the ECI pin (P1.2)
÷
÷
12 (
4 (
÷
÷
2 in X2 mode)
6 in X2 mode)
External I/O Pin
P1.2 / ECI
P1.3 / CEX0
P1.4 / CEX1
P1.5 / CEX2
P1.6 / CEX3
P1.7 / CEX4
4188E–8051–08/06