7721 datasheet(186/577 Pages) RENESAS

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TIMER B

7721 Group User’s Manual

9–19

9.5 Pulse period/Pulse width measurement mode

In this mode, the timer measures an external signal’s pulse period or pulse width. (Refer to “Table 9.5.1.”)

Timers B0 and B1 can be used in this mode. Figure 9.5.1 shows the structures of the timer Bj mode register

and timer Bj register in the pulse period/pulse width measurement mode.

q Pulse period measurement

The timer measures the pulse period of the external signal that is input to the TBjIN pin.

q Pulse width measurement

The timer measures the pulse width (“L” level and “H” level widths) of the external signal that is input

to the TBjIN pin.

Table 9.5.1 Specifications of pulse period/pulse width measurement mode

Item

Count source

Count operation

Count start condition

Count stop condition

Interrupt request occurrence timing

TBjIN pin’s function

Read from timer Bj register

Write to timer Bj register

Timer Bj overflow flagV: The bit used to identify the source of an interrupt request occurrence.

Notes 1: No interrupt request occurs when the first valid edge is input after the counter starts counting.

2: The value read out from the timer Bj register is undefined after the counter starts counting until

the second valid edge is input.

Specifications

f2, f16, f64, or f512

q Countup

q Counter value is transferred to the reload register at valid edge of

measurement pulse, and counting continues after clearing the counter

value to “000016.”

When the count start bit is set to “1.”

When the count start bit is cleared to “0.”

q When valid edge of measurement pulse is input (Note 1).

q When a counter overflow occurs (Timer Bj overflow flagV is set to

“1” simultaneously.)

Measurement pulse input

The value obtained by reading timer Bj register is the reload register’s

contents (Measurement result) (Note 2).

Invalid

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