GMS81C50 Datasheet, PDF (39/99 Pages) Hynix Semiconductor – 8-BIT SINGLE CHIP MICROCONTROLLERS

GMS81C50 Series
HYUNDAI
9.3 R2 Port
R2 is an 8-bit CMOS bidirectional I/O port (address
0C4_H). Each I/O pin can independently used as an input or
an output through the R2DD register (address 0C5_H).
R2 has internal pujll-ups that is independently connected
or disconnected by R2PC (address 0FA_H). The control reg-
isters for R2 are shown as below.
R2 Data Register (R/W)
ADDRESS : 0C4H
RESET VALUE : Undefined
R2
R27 R26 R25 R24 R23 R22 R21 R20
R2 Direction Register (W)
R2DD
ADDRESS : 0C5_H
RESET VALUE : 00_H
Port Direction
0: Input
1: Output
R2 Pull-up Selection Register (W)
R2PC
ADDRESS :0FA_H
RESET VALUE : 00_H
Pull-up select
0: Without pull-up
1: With pull-up
R2 Open drain Assign Register (W)
ADDRESS :0DF_H
RESET VALUE : 00_H
R2ODC
Open drain select
0: Push-pull
1: Open drain
(1) R2 I/O Data Direction Register (R2DD)
R2 I/O Data Direction Register (R2DD) is 8-bit register,
and can assign input state or output state to each bit. If
R2DD is ``1``, port R2 is in the output state, and if ``0``, it
is in the input state. R2DD is write-only register. Since
R2DD is initialized as ``00 h`` in reset state, the whole port
R2 becomes input state.
(2) R2 Data Register (R2)
R2 data register (R2) is 8-bit register to store data of port
R2. When set as the output state by R2DD, and data is writ-
ten in R2, data is outputted into R2 pin. When set as the in-
put state, input state of pin is read. The initial value of R2
is unknown in reset state.
(3) R2 Open drain Assign Register (R2ODC)
R2 Open Drain Assign Register (R2ODC) is 8bit register,
and can assign R2 port as open drain output port each bit,
if corresponding port is selected as output. If R2ODC is
selected as ``1``, port R2 is open drain output, and if select-
ed as ``0``, it is push-pull output. R2ODC is write-only
register and initialized as ``00 h`` in reset state.
(4) R2 Pull-up Resistor Control Register (R2PC)
R2 pull-up resistor control register (R2PC) is 8-bit register
and can control pull-up on or off each bit, if corresponding
port is selected as input. If R2PC is selected as ``1``, pull-
up ia disabled and if selected as ``0``, it is enabled. R2PC
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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