HD643303x Hitachi, HD643303x Datasheet - Page 432

• Manufacturer Part Number: HD643303x
• Description: Hitachi Microcomputer
• Manufacturer: Hitachi

16.4.4 Sample Application of Software Standby Mode
Figure 16-1 shows an example in which software standby mode is entered at the fall of NMI and
exited at the rise of NMI.
With the NMI edge select bit (NMIEG) cleared to 0 in SYSCR (selecting the falling edge), an
NMI interrupt occurs. Next the NMIEG bit is set to 1 (selecting the rising edge) and the SSBY bit
is set to 1; then the SLEEP instruction is executed to enter software standby mode.
Software standby mode is exited at the next rising edge of the NMI signal .
16.4.5 Note
The I/O ports retain their existing states in software standby mode. If a port is in the high output
state, its output current is not reduced.
Clock
oscillator
ø
NMI
NMIEG
SSBY
Figure 16-1 NMI Timing for Software Standby Mode (Example)
NMI interrupt
handler
NMIEG = 1
SSBY = 1
SLEEP
instruction
Software standby
mode (power-
down state)
417
Oscillator
settling time
(t
osc2
)
NMI exception
handling