Samsung SF-335T Repair Manual page 40

3.2.3 I/O PORT configuration and use usage
It has 32 I/O Ports, and 24 Ports of them are arranged to decide I/O direction with Software Control, and the rest 8 Ports are
arranged to be used for Input or Output only. All of I/O Ports are classified into four Blocks according to the characteristics of
I/O Control, and each Block consists of 8 Ports.
Type I/O Control
PA X Byte Control
PB X Byte Control
PC X Byte Control
PD X Byte Control
<1> Assignment of Port PAX
• PA1
• PA2
• PA3
• PA4
• PA5
• PA6
• PA7
<2> Assignment of port PBX
• PB0(Output)
• PB1(Output)
• PB2(Output)
• PB3(Input)
• PB4(Input)
• PB5(Input)
• PB6(Output)
• PB7(Input)
LCD ON/OFF
In case of VCC applied to LCD No. 3 PIN (BACKGROUND LEVEL), all the LCD screen will be erased. When the power is
applied, MICOM PA0~7 are Default High LEVEL, so LCD will be OFF. From Jupiter3, LCD will be ON simultaneously with OPE
reset.
Q1, Q2 have the function of simply doing On/off only.
When pressing the Power Key, actual power is not turned Off but 11.75V terminal of Thundervolt Off in the Main, while simply
the LCD DISPLAY should not appear in OPE. At this point, Micom should be operated normally to recognize the Key when
pressing the Power key again. [The same effect as Power save]
I/O direction USE
I/O => Output LED Control
In : 4, Out : 4 UART, LCD, Sensor
I/O => Input Key Input
I/O => Output LCD Data, Key Scan
: ANSWER LED (RED)
: INK_SAVE LED (GREEN)
: NIGHT_MODE LED (GREEN)
: RESERVED
: SRESERVED
: RESERVED
: RESERVED
* HIGH --> LED OFF
LOW --> LED ON
: LCD Enable
: LCD R/W
: LCD RS
: GND
: Unused (Pull-up)
: GND
: UART TXD in Main UART
: UART RXD from Main UART
CIRCUIT DESCRIPTION
Remarks
Used as LCD VCCCONTROL in MAGIC.
MAGIC SENSOR not applied.