SH7261 datasheet(696/1348 Pages) RENESAS

696 / 1348 page

Section 15 Realtime Clock (RTC)

Rev. 2.00 Sep. 07, 2007 Page 664 of 1312

REJ09B0320-0200

15.4.4

Alarm Function

Figure 15.4 shows how to use the alarm function.

Write 0 to AIE in RCR1

to prevent errorneous interrupt

Clock running

Set alarm time

Disable alarm interrupt

Always clear, since the flag may have been

set while the alarm time was being set.

Write 1 to AIE in RCR1

Clear alarm flag

Enable alarm interrupt

Monitor alarm time

(wait for interrupt or

check alarm flag)

Figure 15.4 Using Alarm Function

Alarms can be generated using seconds, minutes, hours, day of the week, date, month, year, or any

combination of these. Set the ENB bit in the register on which the alarm is placed to 1, and then

set the alarm time in the lower bits. Clear the ENB bit in the register on which the alarm is not

placed to 0.

When the clock and alarm times match, 1 is set in the AF bit in RCR1. Alarm detection can be

checked by reading this bit, but normally it is done by interrupt. If 1 is set in the AIE bit in RCR1,

an interrupt is generated when an alarm occurs.

The alarm flag is set when the clock and alarm times match. However, the alarm flag can be

cleared by writing 0.

SH7261 Datasheet(PDF) 696 Page - Renesas Technology Corp