Panasonic MN101L Series User Manual page 265

Stop the timer when switching the count clock. If the count clock is changed during counting,
the timer doesn't count correctly .
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Do not change the TMnMD.TMnEN simultaneously with other bits to avoid errors in opera-
tion.
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When TMnBC is read on the operation, uncertain value on counting up may be read.
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Writing the value to TMnOC during counting is prohibited.
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The sampled signal of the TMnMD.TMnEN with the count clock controls start/stop of the
binary counter of 8-bit timer on this LSI. Therefore, note the following two points:
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I. To read the binary counter value after the timer has stopped, set the TMnMD.TMnEN to "0",
wait for 1 count cycle, and read the value.
When reading the value without waiting for 1 count cycle, use the program to read the value
of the binary counter multiple times. In this case, the read value is [count value - 1].
II. When changing the timer setting (clock selection, function switching, etc.), wait for 1 count
clock after setting the TMnMD.TMnEN to "0" to stop the timer. Then, Restart the timer.
If the setting is switched during the timer operation, the timer operation is not guaranteed.
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When the value of timer n binary counter matches the setting value of timer n compare regis-
ter, an interrupt request is generated at the next count clock and the timer n binary counter is
cleared. So set the compare register as follows:
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Setting value of the compare register = (counts till the interrupt request) -1
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If the timer interrupt request bit may have already been set before the timer starts, the timer
interrupt request bit should be cleared.
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Chapter 8
8-bit Timer
8-bit Timer VIII - 17