SH7706 Datasheet, PDF (623/749 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family/SH7700 Series

Section 22 Power-Down Modes
Canceling with an Interrupt: The on-chip WDT can be used for hot starts. When the chip detects
an NMI, IRL*¹, IRQ*¹, or on-chip supporting module (except the interval timer)*² interrupt, the
clock will be supplied to the entire chip and software standby mode canceled after the time set in
the WDT's timer control/status register has elapsed. The STATUS1 and STATUS0 pins both go
low. Interrupt processing then begins and a code indicating the interrupt source is set in the
INTEVT and INTEVT2 registers. After branching to the interrupt processing routine occurs, clear
the STBY bit in the STBCR register. The WTCNT stops automatically. If the STBY bit is not
cleared, WTCNT continues operation and transits to the standby mode*³ when it reaches H'80.
This function prevents the data from being destroyed due to a rising voltage under an unstable
power supply. Interrupts are accepted during software standby mode even when the BL bit in the
SR register is 1. If necessary, save SPC and SSR in the stack before executing the SLEEP
instruction. Immediately after an interrupt is detected, the phase of the clock output of the CKIO
pin may be unstable, until the processor starts interrupt processing. (The canceling condition is
that the IRL3 to IRL0 level is higher than the mask level in the I3 to I0 bits in the SR register.)
Notes: 1. Software Standby mode can be canceled using IRL3 to IRL0 or IRQ4 to IRQ0.
2. Software standby mode can be canceled with an RTC or TMU (only when running on
the RTC clock) interrupt.
3. Standby mode should be canceled by power-on resets. Operations at manual resets or
during interrupt input are not guaranted.
WTCNT value
Interrupt
request
WDT overflow and branch to
interrupt handling routine
Crystal oscillator settling
time and PLL synchronization
time
Clear bit STBCR.STBY before
WTCNT reaches H'80. When
STBCR.STBY is cleared, WTCNT
halts automatically.
H'FF
H'80
Time
Figure 22.1 Canceling Software Standby Mode with STBCR.STBY
Canceling with a Reset: Standby mode can be canceled with a reset (power-on or manual). Keep
the RESETP pin and RESETM pin low until the clock oscillation settles.
Rev. 5.00 May 29, 2006 page 575 of 698
REJ09B0146-0500