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User’s Manual U11969EJ3V0UM00
CHAPTER 12 PORT FUNCTION
(2) Setting input/output mode and control mode
The input/output mode of port 4 is set by port mode register 4 (PM4). The control mode (external expansion
mode) is set by mode specification pins MODE and memory expansion mode register (MM: refer to 3.4.6 (1))
(n = 0 to 2).
Port 4 mode register (PM4)
This register can be read/written in 8- or 1-bit units.
Bit Position
Bit Name
Function
7 to 0
PM4n
Port Mode
(n = 7 to 0)
Sets P4n pin in input/output mode.
0: Output mode (output buffer ON)
1: Input mode (output buffer OFF)
Operation mode of port 4
Bit of MM Register
Operation Mode
MM2
MM1
MM0
P40
P41
P42
P43
P44
P45
P46
P47
0
0
0
Port
0
1
1
1
0
0
Address/data bus
1
0
1
(AD0 to AD7)
1
1
1
Others
RFU (reserved)
For the details of mode selection by the MODE pins, refer to 3.3.2 Specifying operation mode.
In the ROM-less mode, MM0 to MM2 bits are initialized to 111 at system reset, enabling the external expansion
mode. External expansion can be disabled by programming the MM0 to MM2 bits and setting the port mode. If MM0
to MM2 are cleared to 000, the subsequent external instruction cannot be fetched.
Address
FFFFF028H
7
PM47
PM4
6
PM46
5
PM45
4
PM44
3
PM43
2
PM42
1
PM41
0
PM40
After reset
FFH
Содержание V854 UPD703006
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