GMS81C50 Datasheet, PDF (37/99 Pages) Hynix Semiconductor – 8-BIT SINGLE CHIP MICROCONTROLLERS

GMS81C50 Series
HYUNDAI
9. I/O PORTS
The GMS81C50 Series has 33 I/O ports which are
PORT0(8 I/O), PORT1 (8 I/O), PORT2 (8 I/O), PORT3 (8
I/O), PORT4 (1 I/O). Pull-up resistor of each port can be
selectable by program. Each port contains data direction
register which controls I/O and data register which stores
port data.
9.1 R0 Ports
R0 is an 8-bit CMOS bidirectional I/O port (address
0C0_H). Each I/O pin can independently used as an input or
an output through the R0DD register (address 0C1_H).
R0 has internal pull-ups that is independently connected or
disconnected by R0PC. The control registers for R0 are
shown below.
R0 Data Register (R/W)
ADDRESS : 0C0_H
RESET VALUE : Undefined
R0
R07 R06 R05 R04 R03 R02 R01 R00
R0 Direction Register (W)
R0DD
ADDRESS : 0C1_H
RESET VALUE : 00_H
Port Direction
0: Input
1: Output
R0 Pull-up Selection Register (W)
R0PC
ADDRESS :0F8_H
RESET VALUE : 00_H
Pull-up select
0: Without pull-up
1: With pull-up
R0 Open drain Assign Register (W) ^{ADDRESS :0E4H}
RESET VALUE : 00_H
R0ODC
Open drain select
0: Push-pull
1: Open drain
(1) R0 I/O Data Direction Register (R0DD)
R0 I/O Data Direction Register (R0DD) is 8-bit register,
and can assign input state or output state to each bit. If
R0DD is ``1``, port R0 is in the output state, and if ``0``, it
is in the input state. R0DD is write-only register. Since
R0DD is initialized as ``00 h`` in reset state, the whole port
R0 becomes input state.
(2) R0 Data Register (R0)
R0 data register (R0) is 8-bit register to store data of port
R0. When set as the output state by R0DD, and data is writ-
ten in R0, data is outputted into R0 pin. When set as the in-
put state, input state of pin is read. The initial value of R0
is unknown in reset state.
(3) R0 Open drain Assign Register (R0ODC)
R0 Open Drain Assign Register (R0ODC) is 8bit register,
and can assign R0 port as open drain output port each bit,
if corresponding port is selected as output. If R0ODC is
selected as ``1``, port R0 is open drain output, and if select-
ed as ``0``, it is push-pull output. R0ODC is write-only
register and initialized as ``00 h`` in reset state.
(4) R0 Pull-up Resistor Control Register (R0PC)
R0 pull-up resistor control register (R0PC) is 8-bit register
and can control pull-up on or off each bit, if corresponding
port is selected as input. If R0PC is selected as ``1``, pull-
up ia disabled and if selected as ``0``, it is enabled. R0PC
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.
9.2 R1 Ports
R1 is an 8-bit CMOS bidirectional I/O port (address
0C2_H). Each I/O pin can independently used as an input or
an output through the R1DD register (address 0C3_H).
R1 has internal pull-ups that is independently connected or
disconnected by register R1PC. The control registers for
R1 are shown below.
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