SH7606 Datasheet, PDF (248/532 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7606 Series

Section 10 Power-Down Modes
10.5.2 Canceling Software Standby Mode
Software standby mode is canceled by interrupts (NMI, IRQ) or a reset.
Canceling with Interrupt: The WDT can be used for hot starts. When an NMI or IRQ interrupt is
detected, the clock will be supplied to the entire LSI and software standby mode will be canceled
after the time set in the timer control/status register of the WDT has elapsed. Interrupt exception
handling is then executed. After the branch to the interrupt handling routine, clear the STBY bit in
STBCR. WTCNT stops automatically. If the STBY bit is not cleared, WTCNT continues
operation and a transition is made to software standby mode* when it reaches H'80. This function
prevents data destruction due to the voltage rise by an unstable power supply voltage.
IRQ cancels the software standby mode when the input condition matches the specified detect
condition while the IRQn1S and IRQn0S bits in IRQCR are not B'00 (settings other than the low
level detection). When the priority level of an IRQ interrupt is lower than the interrupt mask level
set in the status register (SR) of the CPU, the execution of the instruction following the SLEEP
instruction starts again after the cancellation of software standby mode. When the priority level of
an IRQ interrupt is higher than the interrupt mask level set in the status register (SR) of the CPU,
IRQ interrupt exception handling is executed after the cancellation of software standby mode.
Note: * This software standby mode can be canceled only by a power-on reset.
WTCNT value
H'FF
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'80
Time
Figure 10.1 Canceling Standby Mode with STBY Bit in STBCR
Rev. 4.00 Sep. 13, 2007 Page 222 of 502
REJ09B0239-0400