7733 datasheet(194/940 Pages) RENESAS

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TIMER B

7733 Group User’s Manual

7–31

7.5 Pulse period/Pulse width measurement mode

(2) Timer Bi overflow flag

When a measurement pulse’s valid edge is input or an overflow occurs, a timer Bi interrupt request

is generated. The timer Bi overflow flag is used to identify the cause of an interrupt request occurrence,

in other words, determine whether it is an overflow or a valid edge input.

When an overflow occurs, the timer Bi overflow flag is set to “1.” Therefore, the source of the interrupt

request occurrence can be identified by checking the timer Bi overflow flag’s state in the interrupt

routine. The timer Bi overflow flag is cleared to “0” at the next count timing of the count source when

a value is written to the timer Bi mode register with the count start flag = “1.”

The timer Bi overflow flag is a read-only flag.

Do not use this flag for detection of overflow timing.

Figure 7.5.3 shows the operation during pulse period measurement. Figure 7.5.4 shows the operation

during pulse width measurement.

Fig. 7.5.3 Operation during pulse period measurement

Count source

Measurement pulse

Timing when counter is

cleared to “000016”

“1”

“H”

“1”

g The above is applied when measurement is performed from one falling edge of the measurement pulse

until the next falling edge of that.

Reload register @@Counter

Transfer timing

“L”

“0”

Count start flag

“1”

“0”

Initialization of the counter because of measurement completion

Overflow

Cleared to “0” when an interrupt request is accepted;

otherwise, cleared by software

Timer Bi interrupt

request bit

Timer Bi overflow flag

Transferred

(Undefined value)

Transferred

(Measured value)

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