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TIMER B

7733 Group User’s Manual

7–30

7.5 Pulse period/Pulse width measurement mode

7.5.3 Operation in pulse period/pulse width measurement mode

When the count start flag is set to “1,” the counter starts counting of the count source.

When a valid edge of the measurement pulse is input, the counter value is transferred to the reload

After a transfer in , the counter value becomes “000016,” and the counter continues counting.

The timer Bi interrupt request bit is set to “1” when the counter value becomes “000016” in ,(Note).

After this, the interrupt request bit remains set to “1” until the interrupt request is accepted or the

interrupt request bit is cleared to “0” by software.

Operations to are repeated.

Note: Timer Bi interrupt request is not generated when the first valid edge is input after counting starts.

(1) Pulse period/Pulse width measurement

Whether to measure the pulse period or the pulse width of an external signal can be selected by the

measurement mode selection bits (bits 3 and 2 at addresses 5B16 to 5D16). Table 7.5.3 lists the

relationship between the measurement mode selection bits and the pulse period/pulse width measurement.

Make sure that the measurement interval from the falling edge to the rising edge and that of from the

rising edge to the falling edge are two cycles of the count source or more. When measuring pulse

width of a signal whose duty ratio is not 50%, identify whether the measurement result is the “H” level

width or the “L” level width by software.

Table 7.5.3 Relationship between measurement mode selection bits and pulse period/pulse width measurement

Pulse period/Pulse width measurement

Pulse period measurement

Pulse width measurement

Measurement interval (Valid edge)

From falling edge to falling edge (Falling edge)

From rising edge to rising edge (Rising edge)

From falling edge to rising edge, and from rising

edge to falling edge (Falling and Rising edges)

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