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CHAPTER 22 EXTERNAL DEVICE EXPANSION FUNCTION
7
0
Symbol
MM
6
0
5
PW1
4
PW0
3
0
2
MM2
1
MM1
0
MM0
Address
FFF8H 10H
When
Reset
R/W
R/W
MM2 MM1 MM0
Single-chip/
Memory Expansion
Mode Selection
P40-P47, P50-P57, P64-P67 Pin state
P40-P47 P50-P53
P54, P55
P56, P57
P64-P67
000
001
011
100
101
111
Single-chip mode
256-byte
mode
4K-byte
mode
16K-byte
mode
Full
address
mode
Note
Memory
expansion
mode
Port
mode
Input
Output
Port mode
Port mode
Port mode
Port mode
AD0-AD7
A8-A11
A12, A13
A14, A15
P64=RD
P65=WR
P66=WAIT
P67=ASTB
Other than above Setting prohibited
PW1 PW0
00
01
10
11
Wait Control
No wait
Wait (one wait state insertion)
Setting prohibited
Wait control by external wait pin
22.2 External Device Expansion Function Control Register
The external device expansion function is controlled by the memory expansion mode register (MM) and memory
size switching register (IMS).
(1) Memory expansion mode register (MM)
MM sets the wait count and external expansion area, and also sets the input/output of port 4.
MM is set with an 1-bit memory or 8-bit memory manipulation instruction.
RESET input sets this register to 10H.
Figure 22-2. Memory Expansion Mode Register Format
Note The full address mode allows external expansion to the entire 64-Kbyte address space except for
the internal ROM, RAM, and SFR areas and the reserved areas.
Remark P60 to P63 enter the port mode without regard to the mode (single-chip mode or memory expansion
mode).