SH7708 datasheet(356/633 Pages) RENESAS

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12.4

Usage Notes

12.4.1

Flag Clearing

With the SH7708 (not including the SH7708S and SH7708R), the procedure shown in the

flowchart below should be used to clear the carry flag (CF) and alarm flag (AF) in realtime clock

(RTC) register RCR1 (RTC control register 1) and the peripheral interrupt flag (PEF) in register

RCR2 (RTC control register 2).

Wait for 63

µs or more

Entire lot

1. Transition to standby mode

2. Change STC0, STC1 in FEQCR (frequency control register)

3. Change MSTP1 in STBCR (standby control register)

Clear AF flag

Figure 12.6 AF Flag Clearing

If an interval of at least 63 µs is not allowed, the AF flag may not be set even if the setting

conditions are satisfied. Use the same procedure for clearing the CF and PEF flags.

12.4.2

In the SH7708 Series (SH7708, SH7708S, and SH7708R), the following RTC registers cannot be

written to while the RTC is counting (while bit 0 of RCR2 = 1).

RSECCNT, RMINCNT, RHRCNT, RDAYCNT, RWKCNT, RMONCNT, RYRCNT

The RTC count must be stopped before writing to any of these registers.

12.4.3

Usage Note about Periodic Interrupt on RTC

Figure 12.7 shows how to use the periodic interrupt function.

The periodic interrupt function can occur the interrupt periodically which designated by

RCR2.PES bits. RCR2.PEF bit is set to 1 after the period designated by the RCR2.PES bits or

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