Siemens SIMATIC Box PC 820, Manual

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Box PC 820 / PC FI45 V2, Manual
A5E00051531-03
1.5 Point-to-Point Connections
Point-to-Point Connection
In this section, you will learn how to connect your device to a programming device
or programmable controller using a point-to-point connection.
You can establish a point-to-point connection by connecting the SIMATIC PC to a
programming device or a programmable controller via:
S
A V.24 connection.
S
A TTY connection.
Suggestions for Configuring TTY (20 mA) Interfaces
Reliable data transfer depends on several factors. The data transfer rate you can
achieve depends on the distance, the type of cable, the type of interface and any
interference present.
Rules
You can reduce interference by choosing the right transmission cable and
connecting it properly, and observing the following guidelines:
S
Use a shielded cable with a low surge impedance (< 130
W
/ km) and low
capacitance (< 90 pF/m). Twisted-pair cables enhance noise immunity due to
inductance. A low surge impedance results in reduced voltage excursions and
shorter charge reversal times. The larger the conductor cross-section, the lower
the surge impedance for the same length of cable.
S
The shorter the transmission link, the higher the maximum possible data
transfer rate.
S
If there is an active sender and an active receiver at the same end of the
transmission link, the sequence of access priority to the transmission circuit
must be taken into account in order to achieve the longest possible
transmission link.
S
Signal lines and power lines must not be run together. Signal lines must be
installed as far away as possible from strong interference sources
(for example, 400 V three-phase power cables).
S
The active TTY interface with 12 V no-load voltage has been tested on a
1000 m (3300 ft.) long cable at a transmission rate of 9600 bps in a normal
noisy environment (field strength < 3 V/m or 1 V/ft.). If a shielded LiYCY
5x1x0.14 is used, reliable transmission is possible over a distance of up to
1000 m (3300 ft.). The AS511 protocol (only one transmitter at a time) was
used for testing.
Note
The contaminating field of the interference source decreases exponentially with
the distance.
System Unit
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