Schneider Electric LUFP7 user manual Preset Multiple Registers Command 16#10

13. Appendix F: Modbus Commands

13.3. “Preset Multiple Registers” Command (16#10)

Frame	Field	Value or properties
Query	Starting Address (MSB)	- Address of the 1st output / internal register
	Starting Address (LSB)
	Number of Registers (MSB)	- Number of output / internal registers
	Number of Registers (LSB)
	Byte Count	- Number of data bytes = number of output / internal registers × 2
	Data (first register / MSB)	- Byte swap = “No swapping” (or “Swap 2 bytes”)
	Data (first register / LSB)
		- Data length = Value of the “Byte count” field
	………
	Data (last register / MSB)	- Data location = Address in the gateway’s output memory
	Data (last register / LSB)
Response	Starting Address (MSB)	- Address of the 1st output / internal register
	Starting Address (LSB)
	Number of Registers (MSB)	- Number of output / internal registers
	Number of Registers (LSB)

13.4. Modbus Protocol Exception Responses

When it cannot process a command dictated by a Modbus query, a slave sends an exception response instead of the normal response to the query.

With standard Modbus commands, the LUFP7 gateway considers that all exception responses which it receives from Modbus slaves are incorrect responses. As a result, it will carry out the re-transmissions configured for the queries involved.

If you want the software application for your Profibus-DP master to be able to specifically manage exception responses, you can replace the Modbus command, in AbcConf, with a personalized command (see chapter 6.11.3.2 Modbus Commands which Can Be Completely Changed by the User, page 80). This then allows you to feed back the “Slave Address” and “Function” fields to the Profibus-DP master.

The structure of an exception response is independent of the Modbus command associated with the “Function” field of the query involved. The whole frame of an exception response is shown below :

Slave Address

Function

Exception Code

Checksum (Lo)

Checksum (Hi)

Modbus address (1 to 247; addresses 125, 126 and 127 prohibited): The value of this field is identical to that of the “Slave Address” field of the query involved.

Command code, with exception indicator: The value of this field is set to 16#80 + the value of the “Function” field of the query involved.

Code indicating the nature of the error which has caused the exception response (see table on next page).

Error check

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