MC81F4204
90 April 24, 2012 Ver.1.41
14. BASIC INTERVAL TIMER
The MC81F4204 has one 8-bit Basic Interval Timer that is free-run and can not be stopped except
when peripheral clock is stopped.
The Basic Interval Timer generates the time base for watchdog timer counting. It also provides a
Basic interval timer interrupt (BTIF).
The 8-bit Basic interval timer register (BTCR) is increased every internal count pulse which is divided
by prescaler. Since prescaler has divided ratio by 8 to 1024, the count rate is 1/8 to 1/1024 of the
oscillator frequency.
As the count overflow from FFH to 00H, this overflow causes the interrupt to be generated. The Basic
Interval Timer is controlled by the clock control register (CKCTLR).
When write "1" to bit BTCL of CKCTLR, BTCR register is cleared to "0" and restart to count-up. The
bit BTCL becomes "0" after one machine cycle by hardware.
The bit WDTON decides Watchdog Timer or the normal 7-bit timer.
Source clock can be selected by lower 3 bits of CKCTLR.
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