SH7708 Datasheet, PDF (160/625 Pages) Renesas Technology Corp – SuperH™ RISC engine

Table 8.4 Register States in Standby Mode
Module
Registers Initialized
Interrupt controller
Break controller
Bus state controller
On-chip clock pulse generator
Timer unit
Realtime clock
—
—
—
—
TSTR register
—
Registers Retaining
Data
All registers
All registers
All registers
All registers
Registers other than TSTR
All registers
The procedure for moving to standby mode is as follows:
1. Clear the TME bit in the WDT’s timer control register (WTCSR) to 0 to stop the WDT. Set
the WDT’s timer counter (WTCNT) and the CKS2–CKS0 bits of the WTCSR register to
appropriate values to secure the specified oscillation settling time.
2. When PLL circuit 1 is running in clock modes 3–6, clear the PSTBY and PLLEN bits in the
frequency control register (FRQCR) to 0 to stop PLL circuit 1.
3. After the STBY bit in the STBCR register is set to 1, a SLEEP instruction is executed.
4. Standby mode is entered and the clocks within the chip are halted. The STATUS1 pin output
goes low and the STATUS0 pin output goes high.
8 . 4 . 2 Canceling Standby Mode
Standby mode is canceled by an interrupt (NMI, IRL, or on-chip supporting module) or a reset.
Canceling with an Interrupt: The on-chip WDT can be used for hot starts. When the chip
detects an NMI, IRL,^*1 or on-chip supporting module (except the interval timer)^*2 interrupt, the
clock will be supplied to the entire chip and 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 handling then begins and a code indicating the interrupt source is set in the INTEVT
register. Interrupts are accepted during standby mode even when the BL bit in the SR register is 1.
Immediately after an interrupt is detected, the phase of the clock output of the CKIO pin may be
unstable, until the processor starts interrupt handling. (The canceling condition is that the
IRL3–IRL0 level is higher than the mask level in the I3–I0 bits in the SR register.)
Notes: 1. When the RTC is being used, standby mode can be canceled using IRL3–IRL0.
2. Standby mode can be canceled with an RTC or TMU (only when running on the RTC
clock) interrupt.
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