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TIMER A

7733 Group User’s Manual

6–38

6.5.4 Operation in one-shot pulse mode

When the one-shot pulse mode is selected by the operating mode selection bits, pin TAiOUT outputs “L”

level.

When the count start flag is set to “1,” the counter enters the count enable state, and then it starts

counting if a trigger occurs.

When the counter starts counting, pin TAiOUT’s output level becomes “H.” (However, if value “000016”

is set in the timer Ai register, the counter does not operate and the output level of pin TAiOUT remains

“L.” Nor is a timer Ai interrupt request generated.)

When the counter value reaches “000016,” the output level of pin TAiOUT becomes “L.” And then, the

reload register’s contents is reloaded, and the counter stops counting.

Simultaneously with , a timer Ai interrupt request bit is set to “1.”

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.

Figure 6.5.5 shows an operation example in the one-shot pulse mode.

When a trigger occurs after above, the counter and pin TAiOUT perform the same operations beginning

from again. When a trigger occurs during counting, the counter down-counts once after this new trigger

occurs. And then, the reload register’s contents is reloaded and counting is continued. When generating

a trigger during counting, make sure that a certain time which is equivalent to two cycles of the timer’s

count source or more has passed between the trigger previously generated and a new trigger.

The one-shot pulse output from pin TAiOUT can be disabled by clearing the timer Ai mode register’s bit 2

to “0.” Therefore, timer Ai can be used as an internal one-shot timer that does not output the pulse. (In

this case, pin TAiOUT functions as a programmable I/O port.)

6.5 One-shot pulse mode

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