Renesas ZTAT H8S/2357F, Hardware Manual

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Rev.6.00 Oct.28.2004 page 677 of 1016
REJ09B0138-0600H
Oscillator
ø
NMI
NMIEG
SSBY
NMI exception
handling
NMIEG=1
SSBY=1
SLEEP instruction
Software standby mode
(power-down mode)
Oscillation
stabilization
time t
OSC2
NMI exception
handling
Figure 21-2 Software Standby Mode Application Example
21.6.5 Usage Notes
I/O Port Status: In software standby mode, I/O port states are retained. If the OPE bit is set to 1, the address bus and bus
control signal output is also retained. Therefore, there is no reduction in current dissipation for the output current when a
high-level signal is output.
Current Dissipation during Oscillation Stabilization Wait Period: Current dissipation increases during the oscillation
stabilization wait period.
Write Data Buffer Function: The write data buffer function and software standby mode cannot be used at the same time.
When the write data buffer function is used, the WDBE bit in BCRL should be cleared to 0 to cancel the write data buffer
function before entering software standby mode. Also check that external writes have finished, by reading external
addresses, etc., before executing a SLEEP instruction to enter software standby mode. See section 6.9, Write Data Buffer
Function, for details of the write data buffer function.