Conformance Classes

The following Modbus conformance classes (and function codes) are supported by the Modbus/TCP Server and the native Modbus Slave.

·Class 0 (function codes 3 and 16)

·Class 1 (function codes 1, 2, 4, 5, 6, and 7)

·Class 2 (function code 15 only).

Function Code 7

This function code allows a client to request the SCADAPack E Modbus server/slave to return an exception status that is stored in a pre-determined range of 8 coils. RTU binary system (scratchpad) points 50000 to 50007 are allocated for this purpose.

·RTU binary point 50000 will map to the least significant bit of the response byte.

·RTU binary point 50007 will map to the most significant bit of the response byte.

Function Code 8

This function code allows a client to request the SCADAPack E Modbus slave to return a response to a "Return Query Data" request. The following functionality is provided:

·Function Code 8 is supported on Modbus Slave serial connections only

·A Function Code 8 request on a Modbus/TCP connection returns Exception response with error code 1 (Illegal function)

·Sub function 00 00 is the only sub function supported for a Modbus function code 8 request

·A response will only be generated to a FC8 Sub-function 00 00 request when the data field size is 2

·The Response to a FC8 Sub-function 00 00 (data field size 2) request is an echo of the request

·A request for Sub functions other than 00 00 returns an Exception response with error code 3 (Illegal Data Value)

·There will be no response to a FC8 Sub-function 00 00 request if the data field size is not 2

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