Network Design Considerations
2-3
TIWAY 1 Ti505 NIM User Manual
The selection of the network communication media depends primarily on the geographic
distance to be spanned. The main TIWAY I trunk can be up to 10,000 feet long (25,000
feet depending on system loading and baud rate selection), and can have up to 254 drop-
lines. Each dropline can be up to 100 feet long. For distances exceeding 25,000 feet,
RS-232-C/423 media interfaces and modems should be used.
NOTE
The proper installation of your communication media requires careful
planning and design. If you need assistance, a site survey is available
from Siemens Industrial Automation, Inc. Simply fill out and return the
enclosed “TIWAY I Network Evaluation Form”, (Appendix C).
2.1.2
Media Redundancy
Media redundancy is supported for RS-232-C and Local Line NIMs. This means you can
have backup communication media, in case of unforeseen cable problems or accidents. In
order to achieve true redundancy, you must have completely redundant network media
(network trunk lines, tap housings, drop lines, and modems). For example, if you need
Local Line cable redundancy, you will need one PPX:505–7339 TI505 NIM, two separate
twisted pair trunk (spine) cables, and a T-Tap and dropline for each port on the NIM.
The primary reason for using media redundancy is to permit communications on an al-
ternate channel when the main channel fails. The redundant media connection does not
allow two independent networks to communicate with the same NIM.
The NIM will respond over the same channel that received the network command. For
example, if the Host sends the command to Port A, the NIM will respond through Port A.
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