Samsung MSYS 5150 Service Manual

Also see for MSYS 5200: User guide

5-28 Samsung ElectronicsCircuit Description5-4-6 Serial Interface• This part does serial communication with MFPcontroller of the main board (MAIN PBA:U16) thatcontrols the whole system. It controls LIU by givingand taking all control orders and linestatus.• U3-11 RxD : Schmitt Trigger input, Receivingterminal.• U3-29 TxD : Open Drain output terminal• Standard UART communication- Baud Rate : 9600bps- Start, Stop bit : 1bit each- Data bits : 8 bit- Parity bit : none5-4-7 MAJOR FUNCTIONS OF PARTS1) U3 : STI9510-Key part of LIU board. Speech Network,Dialer, Ringer and UART are built in one ICpackage.2) U5 : PC817-Photo coupler. It enables UART ofU3(STI9510) to receive control signal ordialing information from MFP controller ofthe main board (U15).-Insulation Detween prinary and secondanycircuit part.3) U6 : PC817-Photo coupler. It enables UART(U3-29:TxD)of U3(STI9510) to deliver telephone linestatus or response signal about controlsignal or dialing information from LIU MFPcontroller of the main board (U15).-Insulation Detween prinary and secondanycircuit part.4) U4 : PC817-It senses and delivers ring signal to the mainboard.-Insulation Detween prinary and secondanycircuit part.5) U2 : PC814-It senses hook-off (Line connection) of theexternal telephone and delivers it to the mainboard.-Insulation Detween prinary and secondanycircuit part.6) BD1 : BRIDGE DIODE-Regardless of the polarity of DC powerfrom telephone line, the voltage put out onPin.1 has always + polarity against pinPin.2. So DC loop forms always in the samedirection regardless of the polarity of thetelephone line.7) T2,T3 : TRANSFORMER-It delivers signals from the telephone lineto modem or signals from modem to thetelephoneline.-Insulation Detween prinary andsecondany circuit part.