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CHAPTER 5 PORT FUNCTIONS
User’s Manual U12697EJ3V0UM
(2) Pull-up resistor option registers (PU0, PU2, PU3, PU7, PU12, PUO)
These registers are used to set whether to use an on-chip pull-up resistor at each port or not in 1-bit or 8-bit units.
PUn (n = 0, 2, 3, 7, 12) can specify the pull-up resistor connection of each port pin. PUO can specify the pull-
up resistor connection of ports 4, 5, and 6. Pull-up resistors are connected irrespective of whether an alternate
function is used.
These registers are set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets these registers to 00H.
Cautions 1. Ports 1 and 13 do not incorporate a pull-up resistor.
2. Ports 4, 5, and 6 can connect a pull-up resistor during external memory expansion mode.
Figure 5-21. Format of Pull-Up Resistor Option Register
Address: 0FF30H, 0FF32H, 0FF33H, 0FF37H, 0FF3CH After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
PU0
0
0
PU05
PU04
PU03
PU02
PU01
PU00
PU2
PU27
PU26
PU25
PU24
PU23
PU22
PU21
PU20
PU3
PU37
PU36
PU35
PU34
PU33
PU32
PU31
PU30
PU7
0
0
0
0
0
PU72
PU71
PU70
PU12
PU127
PU126
PU125
PU124
PU123
PU122
PU121
PU120
PUxn
Pxn pin pull-up resistor specification
x = 0: n = 0 to 5
x = 2, 3, 12: n = 0 to 7
x = 7: n = 0 to 2
0
No pull-up resistor connection
1
Pull-up resistor connection
Address: 0FF4EH After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
PUO
0
PUO6
PUO5
PUO4
0
0
0
0
PUOn
Port n pull-up resistor specification (n = 4 to 6)
0
No pull-up resistor connection
1
Pull-up resistor connection
Caution Connecting pull-up resistors unnecessarily may increase the current consumption or latch up
other devices, so specify a mode whereby pull-up resistors are only connected to the required
parts. If required and not-required parts exist together, externally connect pull-up resistors to
the required parts and set to the mode that specifies not to connect on-chip pull-up resistors.