Usage Notes - Hitachi H8S/2646 Hardware Manual

Hitachi 16-bit single-chip microcomputer h8s/2646 series
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Oscillator
ø
NMI
NMIEG
SSBY
NMI exception
handling
NMIEG=1
SSBY=1
Figure 22-3 Software Standby Mode Application Example
22.6.5

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 7.7, Write Data Buffer
Function, for details of the write data buffer function.
744
Software standby mode
(power-down mode)
SLEEP instruction
NMI exception
Oscillation
handling
stabilization
time t
OSC2

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