GMS81C50 Datasheet, PDF (40/99 Pages) Hynix Semiconductor – 8-BIT SINGLE CHIP MICROCONTROLLERS

HYUNDAI
GMS81C50 Series
R3 Port
R3 is an 8-bit CMOS bidirectional I/O port (address
0E5_H). Each I/O pin can independently used as an input or
an output through the R3DD register (address 0E6_H).
R3 has internal pull-ups that is independently connected or
disconnected by R3PC (address 0FB_H). The control regis-
ters for R3 are shown as below.
R3 Data Register (R/W)
ADDRESS : 0E5_H
RESET VALUE : Undefined
R3
R37 R36 R35 R34 R33 R32 R31 R30
R3 Direction Register (W)
R3DD
ADDRESS : 0E6_H
RESET VALUE : 00_H
Port Direction
0: Input
1: Output
R3 Pull-up Selection Register (W)
R3PC
ADDRESS :0FB_H
RESET VALUE : 00_H
Pull-up select
0: Without pull-up
1: With pull-up
R3 Open drain Assign Register (W)
ADDRESS :0E0H
RESET VALUE : 00H
R3ODC
Open drain select
0: Push-pull
1: Open drain
(1) R3 I/O Data Direction Register (R3DD)
R3 I/O Data Direction Register (R3DD) is 8-bit register,
and can assign input state or output state to each bit. If
R3DD is ``1``, port R3 is in the output state, and if ``0``, it
is in the input state. R3DD is write-only register. Since
R3DD is initialized as ``00 h`` in reset state, the whole port
R3 becomes input state.
(2) R3 Data Register (R3)
R3 data register (R3) is 8-bit register to store data of port
R3. When set as the output state by R3DD, and data is writ-
ten in R3, data is outputted into R3 pin. When set as the in-
put state, input state of pin is read. The initial value of R3
is unknown in reset state.
(3) R3 Open drain Assign Register (R3ODC)
R3 Open Drain Assign Register (R3ODC) is 8bit register,
and can assign R3 port as open drain output port each bit,
if corresponding port is selected as output. If R3ODC is
selected as ``1``, port R3 is open drain output, and if select-
ed as ``0``, it is push-pull output. R3ODC is write-only
register and initialized as ``00 h`` in reset state.
(4) R3 Pull-up Resistor Control Register (R3PC)
R3 pull-up resistor control register (R3PC) is 8-bit register
and can control pull-up on or off each bit, if corresponding
port is selected as input. If R3PC is selected as ``1``, pull-
up ia disabled and if selected as ``0``, it is enabled. R3PC
is write-only register and initialized as ``00 h`` in reset
state. The pull-up is automatically disabled, if correspond-
ing port is selected as output.
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