CHAPTER 12 PORT FUNCTIONS
User’s Manual U12688EJ4V0UM00
405
12.3.15 Port B
Port B is an 8-bit input/output port that can be set to input or output in 1-bit units.
Address
FFFFF01EH
7
PB7
PB
6
PB6
5
PB5
4
PB4
3
PB3
2
PB2
1
PB1
0
PB0
After reset
Undefined
Bit Position
Bit Name
Function
7 to 0
PBn (n = 7 to 0)
Port B
Input/output port
In addition to their function as port pins, the port B pins can also operate in the control mode (external expansion
mode) as an address bus used when memory is expanded externally.
(1) Operation in control mode
Port
Control Mode
Remark
Block Type
Port B
PB0 to PB7
A8 to A15
Address bus in memory expansion
F
(2) Input/output mode/control mode setting
Port B input/output mode setting is performed by means of the port B mode register (PMB), 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 B mode register (PMB)
This register can be read/written in 8- or 1-bit units.
Address
FFFFF03EH
7
PMB7
PMB
6
PMB6
5
PMB5
4
PMB4
3
PMB3
2
PMB2
1
PMB1
0
PMB0
After reset
FFH
Bit Position
Bit Name
Function
7 to 0
PMBn
(n = 7 to 0)
Port Mode
Sets PBn pin in input/output mode.
0: Output mode (output buffer ON)
1: Input mode (output buffer OFF)
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