
CHAPTER 6 PORT FUNCTIONS
User’s Manual U14800EJ3V0UD
89
(2)
Pull-up resistor option register 0 (PU0)
Pull-up resistor option register 0 (PU0) sets whether an on-chip pull-up resistor on each port is used or not.
On the port specified to use an on-chip pull-up resistor by PU0, the pull-up resistor can be internally used
only for the bits set in the input mode. No on-chip pull-up resistors can be used for the bits set in the output
mode regardless of the setting of PU0. This also applies to cases when the pins are used for alternate
functions.
PU0 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears PU0 to 00H.
Figure 6-12. Format of Pull-Up Resistor Option Register 0
Pm on-chip pull-up resistor selection
(m = 0, 1)
000000
PU01 PU00
PU0
Address
After reset
R/W
FFF7H
00H
R/W
765432
<1>
<0>
PU0m
0
1
On-chip pull-up resistor not used
On-chip pull-up resistor used
Symbol
Caution
Bits 2 to 7 must be set to 0.
(3)
Pull-up resistor option register B2 (PUB2)
Pull-up resistor option register B2 (PUB2) sets whether on-chip pull-up resistors on P20 to P26 are used or
not.
On the port specified to use an on-chip pull-up resistor by PUB2, the pull-up resistor can be internally used
only for the bits set in the input mode. No on-chip pull-up resistors can be used for the bits set in the output
mode regardless of the setting of PUB2. This also applies to cases when the pins are used for alternate
functions.
PUB2 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears PUB2 to 00H.
Figure 6-13. Format of Pull-Up Resistor Option Register B2
P2n on-chip pull-up resistor selection
(n = 0 to 6)
0
PUB26 PUB25 PUB24 PUB23 PUB22 PUB21 PUB20
PUB2
Address
After reset
R/W
FF32H
00H
R/W
7
<6>
<5>
<4>
<3>
<2>
<1>
<0>
PUB2n
0
1
On-chip pull-up resistor not used
On-chip pull-up resistor used
Symbol
Caution
Bit 7 must be set to 0.