Alarm Function; Figure 11.4 Example Of Use Of Alarm Function - Hitachi SH7750 Hardware Manual

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Alarm Function

The use of the alarm function is illustrated in figure 11.4.

Clock running

Disable alarm interrupts

Set alarm time

Clear alarm flag

Enable alarm interrupts

Monitor alarm time

(Wait for interrupt or check

An alarm can be generated by the second, minute, hour, day-of-week, day, month, or year (year is

available only with the SH7750R) value, or a combination of these. Write 1 to the ENB bit in the

alarm registers involved in the alarm setting, and set the alarm time in the lower bits. Write 0 to

the ENB bit in registers not involved in the alarm setting.

When the counter and the alarm time match, RCR1.AF is set to 1. Alarm detection can be

confirmed by reading this bit, but normally an interrupt is used. If 1 has been written to

RCR1.AIE, an alarm interrupt is generated in the event of alarm, enabling the alarm to be

The alarm flag remains set while the counter and alarm time match. If the alarm flag is cleared by

writing 0 during this period, it will therefore be set again immediately afterward. This needs to be

taken into consideration when writing the program.

Rev. 6.0, 07/02, page 288 of 986

Clear RCR1.AIE to prevent erroneous interrupts

Be sure to reset the flag as it may have been

set during alarm time setting

Set RCR1.AIE to 1

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