Sample Application Of Software Standby Mode; Note - Renesas F-ZTAT H8 Series Hardware Manual

Section 21 Power-Down State
21.4.4

Sample Application of Software Standby Mode

Figure 21.1 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.
Clock
oscillator
φ
NMI
NMIEG
SSBY
Figure 21.1 NMI Timing for Software Standby Mode (Example)
21.4.5

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.
Rev. 7.00 Sep 21, 2005 page 672 of 878
REJ09B0259-0700
NMI interrupt Software standby
handler mode (power-
NMIEG = 1 down state)
SSBY = 1
SLEEP
instruction
Oscillator NMI exception
settling time handling
(t )
osc2