CHAPTER 3 CPU FUNCTIONS
User’s Manual U13850EJ4V0UM
91
(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 4 MB. However, the external device cannot be
connected to the internal RAM area, internal peripheral I/O area, and internal ROM area in the single-chip mode
(and even if the external device is connected physically, it cannot be accessed).
The MM register can be read/written in 8- or 1-bit units. However, bits 4 to 7 are fixed to 0.
Figure 3-21. Memory Expansion Mode Register (MM) Format
After reset: 00H
R/W
Address: FFFFF04CH
Symbol
7
6
5
4
<3>
<2>
<1>
<0>
MM
0
0
0
0
MM3
MM2
MM1
MM0
MM3
P95 and P96 operation modes
0
Port mode
1
External expansion mode (HLDAK: P95, HLDRQ: P96)
Note
MM2
MM1
MM0
Address space
Port 4
Port 5
Port 6
Port 9
0
0
0
−
Port mode
0
1
1
64 KB
AD0 to
AD8 to
LBEN,
expansion mode
AD7
AD15
UBEN,
1
0
0
256 KB
A16,
R/W, DSTB,
expansion mode
A17
ASTB,
1
0
1
1 MB
A18,
WRL,
expansion mode
A19
WRH, RD
1
1
×
4 MB
A20,
expansion mode
A21
Other than above
RFU (reserved)
Note
Before switching to the external expansion mode, be sure to set 1 to P95 and P96 of Port 9 (P9).
Remark
For the details of the operation of each port pin, refer to
2.3 Description of Pin Functions
.
Содержание MPD703030A
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