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Siemens S5-135U/155U User Manual

Page 247

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5-107

System Manual
C79000-G8576-C199-06

The TTY submodule feeds in the current (20 mA) via jumpers in the
connector of the standard connecting cable. The 24 V required for generation
of loop current is taken from the power supply of the PLC. In the quiescent
state, with a correct loop current connection, there should be a flow of 20 mA
(= logic 1). When the current is interrupted there is a logic 0.

The following applies to the TTY signals:

Logic 0 is represented by: no current
Logic 1 is represented by: current (20 mA)

A maximum of 9600 bps is permissible for data transmission with the TTY
submodule.

Shown in the figure are the pin assignments of the 25-pin subminiature
D-type connector in the front plate of the TTY submodule:

13

Pin

Designa-
tion

Current
direction

Remarks

25

13

1

Shield

9

24 V
external

This connection is changed over between
24 V internal and 24 V external with
jumper J3 (see next page).

10

+ TxD

²

12

+ 20 mA

³

Current source, transmitter

13

+ RxD

²

14

– RxD

³

14

1

16

+ 20 mA

³

Current source, receiver

1

19

– TxD

³

21

– 20 mA

²

Current return

24

– 20 mA

²

Current return

² : Input

³ : Output

Data Transmission
Rate

Pin Assignments
of the TTY
Submodule

CPUs, Memory Cards, Memory Submodules, Interface Submodules