HD6417705 Datasheet, PDF (419/739 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

15.5 Notes for Usage
15.5.1 Register Writing during RTC Count
The following RTC registers cannot be written to during an RTC count (while the START bit in
RCR2 = 1).
RSECCNT, RMINCNT, RHRCNT, RDAYCNT, RWKCNT, RMONCNT, RYRCNT
The RTC count must be halted 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
interval bits (PES0 to PES2) in RCR2. When the time set by the PES0 to PES2 bits has elapsed,
the PEF bit is set to 1.
The PEF is cleared to 0 upon periodic interrupt generation when the periodic interrupt interval bits
(PES0 to PES2) is set. Periodic interrupt generation can be confirmed by reading this bit, but
normally the interrupt function is used.
Set PES, clear PEF
Set PES0 to PES2,
and clear PEF to 0,
in RCR2
Elapse of time set by PES
Clear PEF
Clear PEF to 0
Figure 15.6 Using Periodic Interrupt Function
15.5.3 Standby Mode after Register Setting
If the standby mode is entered after the RTC registers are set, the time cannot be counted
correctly. After setting the registers, wait for 2 RTC clock cycles or longer before the standby
mode is entered.
Rev. 2.00, 09/03, page 373 of 690