SH7713 datasheet(569/904 Pages) RENESAS

569 / 904 page

Section 15 Realtime Clock (RTC)

Rev.1.50 Aug. 30, 2006 Page 529 of 860

REJ09B0288-0150

15.5

Usage Notes

15.5.1

The following RTC registers cannot be written to during an RTC count (while the START bit = 1

in RCR2).

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

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

15.5.2

Use of Realtime Clock (RTC) Periodic Interrupts

The method of using the periodic interrupt function is shown in figure 15.6.

A periodic interrupt can be generated periodically at the interval set by the periodic interrupt flag

(PES0

−PES2) in RCR2. When the time set by the PES0−PES2 has elapsed, the PEF is set to 1.

The PEF is cleared to 0 upon periodic interrupt generation or when the periodic interrupt flag

(PES0 to PES2) is set. Periodic interrupt generation can be confirmed by reading this bit, but

normally the interrupt function is used.

Set PES0 to PES2,

and clear PEF to 0,

in RCR2

Clear PEF to 0

Set PES, clear PEF

Elapse of time set by PES

Clear PEF

Figure 15.6 Using Periodic Interrupt Function

15.5.3

Transition to Standby Mode after Setting Register

When a transition to standby mode is made after registers in the RTC are set, sometimes counting

is not performed correctly. In case the registers are set, be sure to make a transition to standby

mode after waiting for two RTC clocks or more.

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