12.4.3 Sample Application of Software Standby Mode
In this example the chip enters the software standby mode when NMI goes Low and exits when
NMI goes High, as shown in figure 12-1.
The NMI edge bit (NMIEG) in the system control register is originally cleared to “0,” selecting the
falling edge. When NMI goes Low, the NMI interrupt handling routine sets NMIEG to “1,” sets
SSBY to “1” (selecting the rising edge), then executes the SLEEP instruction. The chip enters the
software standby mode. It recovers from the software standby mode on the next rising edge of
NMI.
Figure 12-1. Software Standby Mode (when) NMI Timing
12.4.4 Application Note
The I/O ports retain their current states in the software standby mode. If a port is in the High
output state, the current dissipation caused by the High output current is not reduced.
Clock
generator
NMI
SSBY
Ø
NMIEG
Settling time
NMI interrupt handler
NMIEG = “1”
SSBY = “1”
Software standby mode
(power-down state)
NMI interrupt handler
SLEEP
244
Summary of Contents for H8/326 Series
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