SH7720 Datasheet, PDF (645/1524 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 17 Realtime Clock (RTC)
17.5 Usage Notes
17.5.1 Register Writing during RTC Count
The following RTC registers cannot be written to during an RTC count (while bit 0 = 1 in RCR2).
RSECCNT, RMINCNT, RHRCNT, RDAYCNT, RWKCNT, RMONCNT, RYRCNT
The RTC count must be stopped before writing to any of the above registers.
17.5.2 Use of Realtime Clock (RTC) Periodic Interrupts
The method of using the periodic interrupt function is shown in figure 17.5.
A periodic interrupt can be generated periodically at the interval set by the flags PES0 to PES2 in
RCR2. When the time set by the PES0 to PES2 has elapsed, the PEF is set to 1.
The PEF is cleared to 0 upon periodic interrupt generation or when the flags PES0 to PES2 are 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 17.5 Using Periodic Interrupt Function
17.5.3 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.
Rev. 3.00 Jan. 18, 2008 Page 583 of 1458
REJ09B0033-0300