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CHAPTER 18 EXTERNAL DEVICE EXPANSION FUNCTION
Preliminary User’s Manual U13420EJ2V0UM00
18.2 External Device Expansion Function Control Register
The external device expansion function is controlled by the following two types of registers.
•
Memory expansion mode register (MEM)
•
Memory expansion wait setting register (MM)
(1) Memory expansion mode register (MEM)
MEM sets the external expansion area.
MEM is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets MEM to 00H.
Figure 18-2. Format of Memory Expansion Mode Register (MEM)
Address: FF47H After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
MEM
0
0
0
0
0
MM2
MM1
MM0
MM2
MM1
MM0
Single-chip/memory
P40 to P47, P50 to P57, P64 to P67 pin state
expansion mode selection P40 to P47 P50 to P53 P54, P55 P56, P57 P64 to P67
0
0
0
Single-chip mode
Port mode
0
0
1
0
1
1
Memory
256-byte
AD0 to AD7 Port mode
P64 = RD
expansion mode
P65 = WR
1
0
0
mode
4-Kbyte
A8 to A11 Port mode
P66 =WAIT
mode
P67 = ASTB
1
0
1
16-Kbyte
A12, A13
Port mode
mode
1
1
1
Full-address
A14, A15
mode
Note
Other than above
Setting prohibited
Note The full-address mode allows external expansion to the entire 64-Kbyte address space except for the internal
ROM, RAM, SFR areas and the reserved areas.
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