Serial Interface - Samsung SF-4500 Service Manual

6-3-6 Serial Interface

• This part does serial communication with MFP
c o n t roller of the main board (MAIN PBA:U16) that
c o n t rols the whole system. It controls LIU by giv-
ing and taking all control orders and line
s t a t u s .
• U 3 - 11 RxD : Schmitt Trigger input, Receiving
t e r m i n a l .
• U3-29 TxD : Open Drain output terminal
• S t a n d a rd UART communication
- Baud Rate : 9600bps
- Start, Stop bit : 1bit each
- Data bits : 8 bit
- Parity bit : none
6-3-7 MAJOR FUNCTIONS OF PARTS
1) U3 : S T I 9 5 1 0
- Key part of LIU board. Speech Network,
D i a l e r, Ringer and UART are built in one IC
p a c k a g e .
2) U5 : PC817
- Photo coupler. It enables UART of
U3(STI9510) to receive control signal or
dialing information from MFP c o n t roller of
the main board (U15).
- Insulation Detween prinary and secondany
c i rcuit part.
3) U6 : PC817
- Photo coupler. It enables UART ( U 3 - 2 9 : T x D )
of U3(STI9510) to deliver telephone line
status or response signal about control
signal or dialing information from LIU MFP
c o n t roller of the main board (U15).
- Insulation Detween prinary and secondany
c i rcuit part.
Samsung Electronics
4) U4 : PC817
- It senses and delivers ring signal to the main
b o a rd .
- Insulation Detween prinary and secondany
c i rcuit part.
5) U2 : PC814
- It senses hook-off (Line connection) of the
external telephone and delivers it to the
main board .
- Insulation Detween prinary and secondany
c i rcuit part.
6) BD1 : BRIDGE DIODE
- R e g a rdless of the polarity of DC power
f rom telephone line, the voltage put out on
Pin.1 has always + polarity against pin
Pin.2. So DC loop forms always in the same
d i rection re g a rdless of the polarity of the
telephone line.
7) T2,T3 : T R A N S F O R M E R
- It delivers signals from the telephone line
to modem or signals from modem to the
t e l e p h o n e
l i n e .
- Insulation Detween prinary and
secondany circuit part.
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