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M30245 Group
4.6 Precautions for External Bus
Description
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Figure 4.6.1. Setting procedure to enter wait mode or stop mode
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
When the MCU enters wait mode while operating in memory expansion mode or micropro-
cessor mode, a pin functioning as part of the address or data bus retains it's state on the bus
before wait mode is entered. Shift to single-chip mode and output an arbitrary value in order
to reduce current consumption. By shifting to single-chip mode, a pin which was functioning
as part of the bus becomes a general-purpose port and can output an arbitrary value. Set
the port registers and direction registers after shifting to single-chip mode (this implies that
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any control pins (CS, WR, RD, etc.. ) being used for access of an external device be
changed as well).
If the port registers and direction registers are set while in memory expansion mode or
microprocessor mode, the operation will be ignored.
This is similar when entering stop mode.
Figure 4.6.1 shows the setting procedure to enter wait mode or stop mode.
Operate in memory expansion mode or microprocessor mode
Shift to single-chip mode
Set the port register
Set the direction register
Enter the wait mode or stop mode
Note 1. This program does not work in external area. Transfer a program
to internal RAM and work on internal RAM.
page 349 of 354
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4. External Buses
Note 1
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