Appendix b. troubleshooting, Appendix b.2. timeout errors on slotserver, Appendix b.3. data transfer – FieldServer FS-RA-CLX-PRO User Manual
Page 9: Appendix b.4. using the output buffer
SlotServer Start-Up Guide
Page 9 of 12
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Appendix B. Troubleshooting
Appendix B.1. Things to check when communications fail.
Check for loose cabling on the third party network
Verify that the correct program is loaded to the CPU
Verify that the correct data types for the tags have been used.
Appendix B.2. Timeout Errors on SlotServer
The following remedial action is suggested if timeout errors are experienced:
The PLC is not set to RUN mode - it may still be in PRG mode. Resolve by putting the PLC into RUN mode.
The IO image connection has not been established successfully. The F screen should show some error
messages also. Refer to the Slotserver Configuration Manual, and insert the correct size and RPI values
when adding the SlotServer in RSLogix5000.
Appendix B.3. Data Transfer
It is important that the PLC is set to Run – data is only transferred on Run.
The SlotServer’s Logix connection will transfer data to the PLC regardless of the Node status of the Client
Nodes. The Logix connection will not be broken if a Client Node goes offline. Node status can be
confirmed by checking the Node Status bits.
Appendix B.4. Using the Output Buffer
The ControlLogix CPU writes the contents of the output buffer into an output buffer image in the SlotServer at a
continuous rate specified by the RPI (Request Packet Interval). This image is in turn transferred into the SlotServer
"Out_xx" Arrays at a continuous rate specified by the output buffer map descriptor. This has the following
consequences:
The Map descriptor has to transfer the output buffer image more often than it is updated (That is, more
often than the RPI), so the scan interval in the output buffer map descriptor must be faster than the RPI.
Out_XX Arrays are written to very frequently. Care must be therefore taken not to attach write on change
map descriptors to the Out_XX Arrays (that is, arrays with functions using rdbc or wrbx), as the write
queues for these writes could build up indefinitely and cause a memory overflow. Using wrbc in these
instances is more sensible and matches the method of writing through the entire process.