NEC 78014Y Series, User Manual

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CHAPTER 19 EXTERNAL DEVICE EXPANSION FUNCTION
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19.2 External Device Expansion Control Register
The external device expansion function is controlled by the memory expansion mode register (MM). MM sets the
wait count and external expansion area. MM also sets the input/output of port 4.
MM is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets this register to 10H.
Figure 19-2. Memory Expansion Mode Register Format
Symbol 7 6 5 4 3 2 1 0 Address When Reset R/W
MM 0 0 PW1 PW0 0 MM2 MM1 MM0 FFF8H 10H R/W
MM2 MM1 MM0 Single-chip/Memory P40 to P47, P50 to P57, P64 to P67 Pins Condition
Expansion Mode Selection P40 to P47 P50 to P53 P54, P55 P56, P57 P64 to P67
0 0 0 Single-chip mode Port Input Port mode
0 0 1 mode Output
0 1 1 Memory 256 bytes AD0 to AD7 Port mode P64 = RD
expansion mode P65 = WR
1 0 0 mode 4 Kbytes A8 to A11 Port mode P66 = WAIT
mode P67 = ASTB
1 0 1 16 Kbytes A12, A13 Port mode
mode
1 1 1 Full-address A14, A15
mode Note
Other than above Setting prohibited
PW1 PW0 Wait Control
0 0 Without wait
0 1 With wait (1 wait state insertion)
1 0 Setting prohibited
1 1 Wait control with an external wait pin
Note The full-address mode allows external expansion to the entire 64 Kbytes address space except for the internal
ROM, RAM and SFR areas and the reserved areas.
Remark P60 to P63 pins enter the port mode regardless of the single-chip mode or memory expansion mode.