SH7018 Datasheet, PDF (397/431 Pages) Renesas Technology Corp – SuperH™ RISC engine

18.4.3 Standby Mode Application Example
This example describes a transition to standby mode on the falling edge of an NMI signal, and a
cancellation on the rising edge of the NMI signal. The timing is shown in figure 18.1.
When the NMI pin is changed from high to low level while the NMI edge select bit (NMIE) of the
ICR is set to 0 (falling edge detection), the NMI interrupt is accepted. When the NMIE bit is set to
1 (rising edge detection) by an NMI exception service routine, the standby bit (SBY) of the
SBYCR is set to 1, and a SLEEP instruction is executed, standby mode is entered. Thereafter,
standby mode is canceled when the NMI pin is changed from low to high level. After the NMI pin
is changed to high level, this level should be held until NMI exception handling begins.
Oscillator
CK
NMI
NMIE
SBY
Oscillation
settling time
NMI Exception
exception service
processing routine
SBY = 1
SLEEP
instruction
Standby Oscillation WDT
mode
start
time
time
set
NMI
exception
processing
Figure 18.1 Standby Mode NMI Timing (Application Example)
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