Numbers of IO modules in a rack in a 800xA System
Would you please tell me that in 800xA system, how much modules (IO modules) can be installed in one rack? And if I use profibus remote IO via CI840 then how much modules can be installed in modulebus right side of FCI?
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Answers
Hope below picture helps you:
For more details, please read S800 I O Fieldbus Communication Interface for PROFIBUS DP DPV1 manual.
If you are using the TB840/TB820 modules, the rules are basically the same as the Profibus segments.
Non-redundant controller allows for a total of 8 I/O segments / 96 modules total(1 local segment to the controller and 7 remote Cluster Modem segments)
Redundant controller allows for a total of 7 I/O segments / 84 modules total(No local segment supported because of redundancy so only 7 remote Cluster Modem segments)
Each TB840/TB820 cluster, in general can allow up to 12 I/O modules per segment (If you are using the redundant I/O bases (2 modules per Termination Base, then you are limited to 6x Termination bases w/ 2 modules per base or 12 in total). As indicated in the initial response to your question, this does vary depending on the I/O module type mix. In particular, the restriction is related to the maximum current draw on the I/O Module Bus. The module that has the largest impact on this draw is the DO820/DO821 (8 Channel Module with Electromechanical Relay: DO820 NO Relay / DO821 NC Relay). Although the S800 Module Bus can support 12 modules per segment, it appears that when using the DO820/DO821 modules, the the maximum number modules per segment if using only DO820/DO821 would be 10.
Additionally, something else to take into consideration when putting your installation together, for the electrical S800 Module bus (ModuleBus Extension Cable Adaptors TB805, TB806 for single ModuleBus) coming off of the controller or the TB840/TB820 or CI840 Profibus modem, the maximum physical length of the bus, including extension cables if used, is 2.5 m (8.2 ft.).
Good luck.
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