7702 datasheet(124/217 Pages) RENESAS

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TIMER A

7702/7703 Group User’s Manual

5–36

5.5 One-shot pulse mode

5.5.4 Operation in one-shot pulse mode

When the one-shot pulse mode is selected with the operating mode select bits, the TAiOUT pin outputs

“L” level.

When the count start bit is set to “1,” the counter is enabled for counting. After that, counting starts when

a trigger is generated.

When the counter starts counting, the TAiOUT pin outputs “H” level.

When the counter value becomes “000016,” the output from the TAiOUT pin becomes “L” level. Additionally,

the reload register’s contents are reloaded and the counter stops counting there.

Simultaneously at , the timer Ai interrupt request bit is set to “1.”

This interrupt request bit remains set to “1” until the interrupt request is accepted or the interrupt request

bit is cleared to “0” by software.

Figure 5.5.5 shows an example of operation in the one-shot pulse mode.

When a trigger is generated after above, the counter and TAiOUT pin perform the same operations

beginning from again. Furthermore, if a trigger is generated during counting, the counter down-counts

once after this generated new trigger, and it continues counting with the reload register’s contents reloaded.

If generating a trigger during counting, make sure that a certain time which is equivalent to one cycle of

the timer’s count source or more has passed between the previous generated trigger and a new generated

trigger.

The one-shot pulse output from the TAiOUT pin can be disabled by clearing the timer Ai mode register’s bit

2 to “0.” Accordingly, timer Ai can be also used as an internal one-shot timer that does not perform the

pulse output. In this case, the TAiOUT pin functions as a programmable I/O port.

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