HD6433308 Datasheet, PDF (266/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

14.4.1 Transition to Software Standby Mode
To enter the software standby mode, set the standby bit (SSBY) in the system control register
(SYSCR) to “1,” then execute the SLEEP instruction.
14.4.2 Exit from Software Standby Mode
The chip can be brought out of the software standby mode by an input at one of six pins: NMI,
IRQ0, IRQ1, IRQ2, RES, or STBY.
(1) Recovery by External Interrupt: When an NMI, IRQ0, IRQ1, or IRQ2 request signal is
received, the clock oscillator begins operating. After the waiting time set in the system control
register (bits STS2 to STS0), clock pulses are supplied to the CPU and on-chip supporting modules.
The CPU executes the interrupt-handling sequence for the requested interrupt, then returns to the
instruction after the SLEEP instruction. The SSBY bit is not cleared.
See Section 14.2, “System Control Register: Power-Down Control Bits” for information about the
STS bits.
Interrupts IRQ3 to IRQ7 should be disabled before entry to the software standby mode. Clear
IRQ3E to IRQ7E to "0" in the interrupt enable register (IER).
(2) Recovery by RES Pin: When the RES pin goes Low, the clock oscillator starts. Next, when
the RES pin goes High, the CPU begins executing the reset sequence. The SSBY bit is cleared to
“0.”
The RES pin must be held Low long enough for the clock to stabilize.
(3) Recovery by STBY Pin: When the STBY pin goes Low, the chip exits from the software
standby mode to the hardware standby mode.
14.4.3 Sample Application of Software Standby Mode
In this example the H8/330 enters the software standby mode when NMI goes Low and exits when
NMI goes High, as shown in Figure 14-1.
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