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TIMER B

7733 Group User’s Manual

7–33

7.5 Pulse period/Pulse width measurement mode

[Precautions in pulse period/pulse width measurement mode]

1. A timer Bi interrupt request is generated by the following sources:

q The measurement pulse’s valid edge which is input

q An overflow

The interrupt request source shown above can be determined by the timer Bi overflow flag.

2. At reset, the timer Bi overflow flag is set to “1.” This flag can be cleared to “0” by performing writing

to the timer Bi mode register with the count start flag = “1.”

3. When the first valid edge is input after counting starts, an undefined value is transferred to the reload

4. At start of counting, the counter value is undefined. Therefore, there is a possibility that a timer Bi

interrupt request is generated by an overflow which occurs immediately after counting starts.

5. When the measurement mode selection bits are changed after counting starts, the timer Bi interrupt

request bit is set to “1.” Note that the timer Bi interrupt request bit does not change if the same value

as before is written to the measurement mode selection bits.

6. When an input signal to pin TBiIN is affected by noise or others, there is a possibility that the counter

cannot perform the exact measurement. We recommend to verify, by software, that the measurement

values are within a constant range.

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