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(1) Memory expansion mode register (MM)
This register sets the mode of each pin of ports 4, 5, 6, and 9. In the external expansion mode, an external
device can be connected to the external memory area of up to 16 Mbytes. However, the external device cannot
be connected to the internal RAM area, peripheral I/O area, and internal ROM area in the single-chip mode
(access is restricted to external locations 100000H through FFE00H).
The MM register can be read/written in 8- or 1-bit units. However, bits 4 to 7 are fixed to 0.
7
6
MM
0
0
Bit Position
Bit Name
3
MM3
2 to 0
MM2 to MM0
Remark For the details of the operation of each port pin, refer to 2.3 Pin Function.
68
CHAPTER 3 CPU FUNCTIONS
5
4
3
2
0
0
MM3
MM2
Memory Expansion Mode
Specifies operation mode of P95 and P96 of port 9.
MM3
Operation Mode
0
Port mode
1
External expansion mode
Memory Expansion Mode
Specifies operation mode of ports 4, 5, 6, and 9 (P90 to P94).
MM2
MM1
MM0
Address
Space
0
0
0
0
1
1
expansion
1
0
0
256-KB
expansion
1
0
1
expansion
1
1
0
expansion
1
1
1
16-MB
expansion
Others
User's Manual U11969EJ3V0UM00
1
0
Address
MM1
MM0
FFFFF04CH
Function
P95
P96
Port
HLDAK HLDRQ
Port 4
Port 5
–
Port mode
64-KB
AD0 to
AD8 to
AD7
AD15
1-MB
4-MB
RFU (reserved)
After reset
07H (in ROM-less mode)
00H (in single-chip mode)
Port 6
Port 9
(P90 to P94)
LBEN,
UBEN,
A16
R/W,
A17
DSTB,
A18
ASTB,
A19
WRL,
A20
WRH,
A21
A22
RD
A23
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