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TIMER B

7721 Group User’s Manual

9–21

9.5 Pulse period/Pulse width measurement mode

9.5.1 Setting for pulse period/pulse width measurement mode

Figure 9.5.2 shows an initial setting example for registers relevant to the pulse period/pulse width measurement

mode.

Note that when using interrupts, set up to enable the interrupts. For details, refer to “CHAPTER 7.

INTERRUPTS.”

Fig. 9.5.2 Initial setting example for registers relevant to pulse period/pulse width measurement mode

Count starts

Measurement mode select bits

Selecting pulse period/pulse width measurement mode and each function

Timer Bj mode register (i = 0, 1) (Addresses 5B16, 5C16)

Setting count start bit to “1”

Count start register (Address 4016)

Timer B0 count start bit

Timer B1 count start bit

b3 b2

Count source select bits

b7 b6

Timer Bj overflow flag (Note)

0: No overflow

1: Overflowed

Setting port P5 direction register

Port P5 direction register (Address D16)

Clear the corresponding bit to “0.”

TB0IN pin

TB1IN pin

0 0 : Pulse period measurement (Interval between falling edges

of measurement pulse)

0 1 : Pulse period measurement (Interval between rising edges

of measurement pulse)

1 0 : Pulse width measurement

1 1 : Do not select.

0 0 : f2

0 1 : f16

1 0 : f64

1 1 : f512

Note: The timer Bj overflow flag is a read-only bit. This bit is undefined after reset. When a value is written to the timer Bj mode register with

the count start bit = “1,” this bit is cleared to “0” at the next count timing of the count source.

Setting interrupt priority level

Timer Bj interrupt control register (j = 0, 1)

(Addresses 7A16, 7B16)

Interrupt priority level select bits

When using interrupts, set these bits to one of levels

1 to 7.

When disabling interrupts, set these bits to level 0.

Selection of pulse period/pulse width measurement mode

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