TIMER-COUNTERS

There are two hardware timers; one is 8-bit and the other 16-bit. The former can be clocked internally at 814ns, 6.51�s or 104�s or it can use an external clock enabling it to be used as an external event counter. The 16-bit counter increments every 814ns.

See 6301 MICROPROCESSOR DATA for full information on how to use the timer-counters.

The timer-counters can be read and written by software and each may generate an interrupt on overflow to allow extension to 32-bit counting and beyond. The 16-bit timer has two output capture registers which can raise a flag when the counter matches the output capture value. These can be polled or used to cause interrupts, or generate a hardware output. The 16-bit timer also has an input capture mode; on receipt of an external signal the counter value is transferred to a 16-bit register so that the exact transition time can be read by software.

This table shows how supplied software uses the timer-counters:

FACILITY		USED BY	PURPOSE

16-bit Timer
	Overflow Interrupt	Forth ROM	date & time
	Output Compare 1	Forth ROM	regular interrupts in Forth
		_EVERY.TDS	execution at defined intervals
		_SERIAL2.TDS	serial port 2
	Output Compare 2	Not used
	Input Capture	Not used

8-bit Timer	Not used*

* Unless serial port 1 has a baud rate other than 300, 1200, 9600 or 76800.

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