FieldServer FS-8704-14 instruction manual FieldServer as a Client

FS-8704-14 EtherNet/IP Manual		Page 23 of 30
Appendix A.6.2.	The PLC Program

The PLC program example below shows the minimum steps necessary to program communications with the FieldServer. Depending on the real intended application, additional steps may be necessary for completeness.

When the FieldServer is polling the PLC, all that is needed is to configure the tags being accessed:

Step 2

Tag Length must be equal to or greater than the number of points being written/read

Avoid Using UDT Types. The Data will be read but the exact placement of the data in the Tags and Arrays will be hard to determine

Note that providing dedicated (long), flat structured (not UDT) tags for communicatons interface to the FieldServer is preferable to polling single length tags in the PLC as it allows for much more efficient communications and reduces complexity when mapping data in the FieldServer. It is better to think of these tags as a “I/O Buffer” Interface that the real tags in the PLC get mapped to.

Appendix A.7. Read/write structures and value of EIP_Structure_Handle :

Some devices require that a specific value be used for the EIP_Structure _Handle field while writing the structure to them. This value may be specified in the vendor documentation. If any non-zero integer is used in a Read Map Descriptor for EIP_Structure_Handle, the value will be updated internally. The Map Descriptor can then be browsed to obtain this value. Other devices do not validate this field when the structure is written by the third- party device. A summary of the procedures to obtain this value is presented below:

FieldServer as a Client:

Read:

Use a value of 1, the driver will automatically update the field when a response is received from the device. The Map Descriptor can then be browsed to obtain the value if required.

Write:

Use the value supplied by the vendor OR

Use the value obtained in the Read Map Descriptor above OR Use any non-zero value if the other device doesn’t validate it.

FieldServer as a Server:
Read:
Use the value supplied by the vendor OR
Use the value obtained in the Read Map Descriptor above OR
Use any value if the other device doesn’t validate it.
Write:
Not required – use any	non-zero value if	the parameter is specified.
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