87
CHAPTER 4 I/O PORTS
Table 4.3-3 lists the functions of port 3 registers.
Port 3 pull-up setting register (PUL3)
The bits of the pull-up setting register correspond to the pins of port 3 in one-to-one correspondence. When
the pull-up resistor is selected by using the pull-up setting register, the pin state will be "H" level (pull-up
state) instead of Hi-Z during stop (SPL = 1). During a reset, however, the pull-up is invalid and the pin
remains at Hi-Z.
Figure 4.3-2 shows the pull-up resistor settings assigned to the values of the bits of the port 3 pull-up
register.
Figure 4.3-2 Pull-up Setting Register (PUL3)
Table 4.3-3 Functions of Port 3 Registers
Register
name Data When being
read When being written Read/
Write Address Initial value
Port 3 data
register
(PDR3)
0Pin state is
"L" level.
Output latch of "0" is set and
"L" level is output to the pin in
output port mode. R/W 000CHXXXXXXXXB
1Pin state is
"H" level.
Output latch of "1" is set and
"H" level is output to the pin in
output port mode.
Port 3 data
direction
register
(DDR3)
0Read
prohibited
(write only)
Output transistor operation is
disabled and the pin is set to
serve as an input pin. W000D
H00000000B
1Output transistor operation is
enabled and the pin is set to
serve as an output pin.
R/W : Readable and Writable
W : Write only
X : Undefined
PUL33 PUL32 PUL31 PUL30
0
1
PUL37 PUL36 PUL35 PUL34
0
1
bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0
0071HPUL37 PUL36 PUL35 PUL34 PUL33 PUL32 PUL31 PUL30 00000000B
R/W R/W R/W R/W R/W R/W R/W R/W
R/W : Readable and Writable
: Initial value
Address Initial value
P33 pull-up OFF P32 pull-up OFF P31 pull-up OFFP30 pull-up OFF
P33 pull-up ON P32 pull-up ON P31 pull-up ON P30 pull-up ON
P37 pull-up OFF P36 pull-up OFF P35 pull-up OFF P34 pull-up OFF
P37 pull-up ON P36 pull-up ON P35 pull-up ON P34 pull-up ON