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(2) Input/output mode/control mode setting
Port 4 input/output mode setting is performed by means of the port 4 mode register (PM4), and control mode
(external expansion mode) setting is performed by means of the mode specification pins (MODE0 to MODE3)
and the memory expansion mode register (MM: refer to 3.4.6 (1)).
(a) Port 4 mode register (PM4)
This register can be read/written in 8- or 1-bit units.
7
6
PM4
PM47
PM46
Bit Position
Bit Name
7 to 0
PM4n (n = 7 to 0)
(b) Operation mode of port 4
Bit of MM Register
MM3
MM2
MM1
don't
0
0
care
0
0
0
1
0
1
1
0
1
0
1
1
1
1
For the details of mode selection by the MODE0 to MODE3 pins, refer to 3.3.2 Operating mode
specification.
In ROM-less modes 0 or 1, or single-chip mode 1, the MM0 to MM3 bits are initialized to 111× at system
reset, enabling the external expansion mode. External expansion can be disabled by programming the
MM0 to MM3 bits and setting the port mode. If MM0 to MM3 are set to 000×, the subsequent external
instruction cannot be fetched.
Remark ×: don't care
CHAPTER 12 PORT FUNCTIONS
5
4
3
PM45
PM44
PM43
Port Mode
Sets P4n in input/output mode.
0: Output mode (output buffer ON)
1: Input mode (output buffer OFF)
MM0
P40
P41
0
1
0
1
0
1
0
1
User's Manual U12688EJ4V0UM00
2
1
0
PM42
PM41
PM40
Function
Operation Mode
P42
P43
P44
Port (P40 to P47)
Data bus (D0 to D7)
Address
After reset
FFFFF028H
FFH
P45
P46
P47
381
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