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8-bit Timers
10-29
Differences between using a timer as a prescaler and when cascaded
The following explanation of these differences uses the cases where the clock source for timer 1 is set to "timer 0
underflow" and to "cascaded with timer 0" as examples.
When "timer 0 underflow" is set, operation is as shown in Fig. 10-6-6. (IOCLK is selected as the clock source for
timer 0.)
When TM0BC underflows, the value that is set in TM0BR is loaded into TM0BC, and the value in TM1BC is
decremented by one.
When TM1BC underflows, the value that is set in TM1BR is loaded into TM1BC.
TM0BC value
Interrupt request
signal (TM1IRQ)
TM1BC value
x'00x'01
TM0BR value
TM0BR value-1
IOCLK
x'00x'01
TM0BR value
TM0BR value-1
x'00x'01
TM0BR value
Interrupt request
signal (TM0IRQ)
x'00x'01
TM1BR value
Fig. 10-6-6 Operation of Timers 0 and 1 (1)