Siemens Simatic S7-300 CP 341 - 20 Ma-TTY Interface of the CP 341-20 Ma TTY; Table 1- 5 RS 232 C Interface Signals

Product Description
1.4 Properties of the Serial Interface
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
Manual, 09/2008, A5E02191071-01 25
RS 232C signals
The following table shows the meanings of the RS232C accompanying signals.
Table 1- 5 RS 232C interface signals
Signal Designation Meaning
TXD Transmitted Data Transmitted data; Transmission line is held by CP 341 on logic "1" in idle state.
RXD Received Data Received data; Receive line must be held on logic "1" by communication partner.
RTS Request To Send RTS "ON": CP 341 ready to send
RTS "OFF": CP 341 is not sending
CTS Clear To Send Communication partner can receive data from the CP 341. The communication
processor expects the signal as response to RTS "ON".
DTR Data Terminal Ready DTR "ON": CP 341 is switched on and ready for operation
DTR "OFF": CP 341 is not switched on and is not ready for operation
DSR Data Set Ready DSR "ON": Communication partner is switched on and ready for operation
DSR "OFF": Communication partner is not switched on and not ready for operation
RI Ring Indicator Incoming call on connection of a modem
DCD Data Carrier Detect Carrier signal on connection of a modem
1.4.2 20mA-TTY interface of the CP 341-20mA TTY
Definition
The 20mA-TTY interface is a current-loop interface used for serial data transmission.
Properties
The 20mA-TTY interface has the following properties and meets the following requirements:
Type: Current-loop interface
Front connector: 9-pin subminiature D female with screw interlock
20mA TTY signals: two isolated 20 mA current sources, receive loop (RX) "-" and "+" transmit
loop (TX) "-" and "+"; all isolated against the S7-internal power supply
(S7-300 backplane bus) and the external 24 V DC supply
Max. baud rate: 19.2 kbaud
Max. cable length: 1000 m active at 9.6 kbaud
1)
(CP supplies the current loop), 1000 m passive
at 9.6 kbaud
1)
(partner supplies the current loop), 500 m active, 500 m
passive at 19.2 kbaud; cable type LIYCY 7 x 0.14 (6ES7902-2Ax00-0AA0)
Standard: DIN 66258 Part 1
1)
The switch from active to passive is made possible through appropriate wiring on the cable
connector.
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