Can a BMXNOM0200 module be changed programmatically from Client to Server in a X80 EIO drop?

Title


Issue


Product Line
Applicable product lines.

Environment
Vendor, Product, Version

Cause
N/A

Resolution
To configure the BMXNOM0200 as a Modbus RS-485 RTU Server in an X80 drop, use these firmware versions or higher:
BMXCRA31210.3 SV ≥ V2.12
BMXNOM0200.4 SV ≥ V1.5

In X80 EIO drops, Modbus server messages received by the BMXNOM0200.4 module are transferred through the X80 EIO adapter module (BMXCRA31210.3 or BMECRA31210).
The BMXNOM0200.4 module is configured differently in an M580 X80 drop than Quantum RIO drop, and is compatible with M580 BME•58••40 CPUs.

For the BMXNOM0200.4 module:
Channel 0 supports RS-232 or RS-485.
Channel 1 supports only RS-485.

Declaring the BMXNOM0200 module as a BMXNOM0200.4 module in Unity Pro allows you to configure the module for: Modbus RTU server on RS-485

NOTE:
Only Modbus RTU is supported as server protocol.
Only RS-485 is supported when Modbus server is selected


The READ_STS_MX function block is used to read the status words of an (e)X80 local rack or Ethernet RIO module, by performing an explicit exchange with the CPU memory.
These status words contain data on the operating mode of the module, and may be used to perform program-based diagnostics.

The WRITE_CMD_MX function block can be used to send a command to an (e)X80 local rack or Ethernet RIO module through the use of command words, by performing an explicit exchange.

To change the protocol used by a BMX NOM 0200 serial communication using the WRITE_CMD*(IODDT_VAR1) command.
This command can be used to switch between the following three protocols:
Modbus Server
Modbus Client
Character Mode

You must create first an IODDT variable linked to the serial channel, then set to 1 the bit of word IODDT_VAR1.CONTROL (%MWr.m.c.24) that corresponds to the change of protocol desired:
NOTE: IODDT_VAR1 variable must be either a T_COM_MB_BMX or a T_COM_MB_BMX CONF EXT type.
TO_MODBUS_MASTER (Bit 12): Current protocol is changed to Modbus Client.
TO_MODBUS_SLAVE (Bit 13): Current protocol is changed to Modbus Server.
TO_CHAR_MODE (Bit 14): Current protocol is changed to Character Mode.

Three protocol changes are used:
1. Transfer from Modbus Server to Modbus Client:
The aim of Modbus Client configuration is to send information about an event to another PLC. When a change is made from Modbus Server configuration to Modbus Client configuration, transmission, signal and physical line parameters remain the same. Only the values of the following parameters specific to Modbus Client configuration are changed:
The Delay Between Frames is set to its default value, which depends on transmission speed.
Answer delay is set to 3 s
Number of retries set to 0

2. Transfer from Modbus Client/Server to Character Mode
Switching to Character Mode is used to send AT commands to a modem. When a change is made from Modbus configuration to Character Mode configuration, transmission, signal and physical line parameters remain the same. Only the message end detection parameter specific to Character Mode is set to stop on reception of the x0d ending character.

3. Transfer from Character Mode to Modbus Client/Server:
The aim of Character Mode configuration is to communicate with a private protocol (a modem, for instance). Once the exchange has finished, the user switches to the Modbus Client configuration (with the answer delay set to 3 s and the number of retries set to 0) in order to send information about an event to another PLC. Once the message has been sent, the user returns to the Modbus Server configuration: the node number is set to the value stored in the FLASH memory or to 248 if none.

NOTE: Be careful that two clients (on the same bus) do not send requests simultaneously otherwise the requests are lost and each report will have a bad result which could be 16#0100 (request could not be processed) or 16#ODFF (server is not present).

Released for:Schneider Electric Hong Kong