Schneider Electric LUFP7 user manual Bits Description Abcdu Modbus exchanges activated

5. Gateway Initialization and Diagnostics

Bits Description

13ABC_DU: Modbus exchanges activated

The gateway activates this bit to tell the Profibus-DP master that the Modbus data located in its input memory area have all been updated at least once since the last activation of FB_DU (“ABC_DU” means “ABC – Data Updated”). These Modbus input data include every data in responses from all Modbus slaves, for both periodic commands and aperiodic commands.

This bit is deactivated by the gateway when the FB_DU bit is deactivated, that is to say when the Profibus-DP master demands a shutdown of Modbus exchanges.

N.B. Once it is active, this bit is not deactivated if there are any communication errors with the Modbus slaves. To signal this type of error, the gateway uses bit 12 of its status word.

12Periodicity of Modbus exchanges

The gateway activates this bit provided that it is periodically communicating with all of the Modbus slaves. It deactivates it as soon as it loses communication with one of them.

The “Reconnect time (10ms)”, “Retries” and “Timeout time (10ms)” elements of each of the Modbus queries (see chapter 6.11.2.2 Configuring the Query, page 72) are used to determine whether communication is lost, then restored.

N.B. If a number of periodic exchanges are configured for the same Modbus slave, only one of them needs to remain active for the periodic communications with this slave to be declared active.

8-11EC: Error code associated with the Modbus network

Code of the error detected on the Modbus network by the gateway and transmitted to the Profibus- DP master.

0- 7 ED: Error data item associated with the Modbus network

Data item associated with the EC error code.

The correct use of this status word by the Profibus-DP master, to read a diagnostic generated by the gateway, goes through the following steps:

•Checking of (ABC_HS_SEND ≠ FB_HS_CONFIRM).

• Reading of the value of ABC_DU to determine whether all of the Modbus input data are up-to-date.

• Reading of the value of the “Periodicity of Modbus exchanges” bit to determine whether the periodicity of the Modbus communications has been maintained.

• Reading of the values of EC and ED to check for any error detected by the gateway on the Modbus network (see table page 41).

• Copying of the value of the ABC_HS_SEND bit to the FB_HS_CONFIRM bit.

This last step is essential because it allows the gateway to transmit a future diagnostic in order not to “loose” any further error reporting! Even if you do not wish to read the content of the gateway’s status word, it is preferable to automate this step in your Profibus-DP master software.

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