CTI 2500-RIO-B Installation and Operation Guide V1.4
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APPENDIX A. REMOTE I/O INSTALLATION GUIDELINES
These Remote I/O Installation Guidelines are based on standard RS485 wiring practices. See
Chapter 6 of the SIMATIC® 505 545/555/575 System Reference Manual for further details.
The Remote I/O cable system consists of a main trunk line and drop lines which connect the
CPU/Local Base and Remote Base(s) to the trunk line by means of terminal blocks as shown in
Figure 5.
Local Base
T
T
T
Remote Base
Remote Base
Trunk Lines
Drop Lines
Drop Line
T = Terminal Block
Figure 5. Remote I/O Installation
Cable Layout Planning
Use the following guidelines for planning the Remote I/O cable routing and locations:
•
The ideal cable installation is a single, unbranched trunk line with short drop lines and
termination resistor at each end
•
Maximum length of a drop line should not exceed 33 feet (10 m)
•
Drop lines less than 3.3 feet (1 m) do not count toward cable length calculations
•
The total length of all drop lines should be much less than the length of the trunk line
•
When multiple bases must be located in close proximity, connect all bases in a “daisy-chain”
arrangement with a single drop line.
Cable Selection
Data transfer in the Remote I/O systems is based on a symmetrical RS485 bus system using shielded
twisted pair cable. The cable shield is used to improve the immunity to electromagnetic interference.
The ideal cable provides low signal attenuation for long trunk lines and flexibility for ease of
installation. The recommended cable should include the characteristics as shown in the following
table.
