GMS81C50 datasheet(39/99 Pages) HYNIX

39 / 99 page

GMS81C50 Series

HYUNDAI

9.3 R2 Port

R2 is an 8-bit CMOS bidirectional I/O port (address

0C4H). Each I/O pin can independently used as an input or

an output through the R2DD register (address 0C5H).

R2 has internal pujll-ups that is independently connected

or disconnected by R2PC (address 0FAH). The control reg-

isters for R2 are shown as below.

(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

(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.

R2 Data Register (R/W)

ADDRESS : 0C4H

RESET VALUE : Undefined

R27 R26 R25 R24 R23 R22 R21 R20

Port Direction

R2 Direction Register (W)

R2DD

ADDRESS : 0C5H

RESET VALUE : 00H

0: Input

1: Output

Pull-up select

R2 Pull-up Selection Register (W)

R2PC

ADDRESS :0FAH

RESET VALUE : 00H

0: Without pull-up

1: With pull-up

Open drain select

R2 Open drain Assign Register (W)

R2ODC

ADDRESS :0DFH

RESET VALUE : 00H

0: Push-pull

1: Open drain

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