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Appendix C.8. Stuck Unit.
Communications on the DAP units requires the operation of a mechanical relay. This can get stuck. The Front Panel menu of each DAP unit allows a user to execute a diagnostic test of the comms board. The customer should execute this test and use the Data Aire installation guide to resolve any issues. Typically a failed unit requires replacement. A single failed card will fail the whole network. The FieldServer sends polls on the primary port and expects responses on the secondary port. The fact that we get back a copy of the poll message on the secondary port does not mean that the units are operating correctly since this is possible when the units are stuck in pass thru mode.
Appendix C.9. Number of Units
Up to 250 DAP devices can be connected to a FieldServer using the DAP driver.
Normal RS485 network considerations apply - these limit the number of units based on the load of each node.
•For unit loads only 32 devices per network can be used.
•For .25 unit loads 128 devices can be used on one network segment. If more than 32 full unit loads are required then the network must be segmented and connected via a repeater
•It may be necessary to use a repeater if total
It is recommended that tests are performed with a single or few units.
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