Modbus RTU Slave Broadcast

[marioschranz]

Hello everyone

I am having trouble implementing a Modbus RTU Slave on my PIC18F66K22 with Flowcode 10.

The component I am using in Flowcode 10 is the Modbus Slave 2.0 component for creating Modbus compatible slave hardware via RS232 or RS485.

Read/Write querys with any unit ID from 1 to 247 are working fine and I am able to map the received data in the holding registers back to the master using other addresses in the holding registers.

Using unit ID 0 for broadcast messages I do not receive any data on the slave. Neither do I get an error on the master or slave.
Are broadcast messages supported with the Modbus Slave component and are there any restrictions regarding the function codes?

Kind regards
Mario

[BenR]

Hi Mario,

Broadcast messages are currently not supported we currently only respond to a matching ID.

Is address 0 typically used for broadcast messages? If so how do the slave devices deal with responding so as to not collide with each other?

[marioschranz]

Hi Ben

Thanks for your reply.

Yes with Modbus address 0 is used for broadcast messages from master to slave. Slaves do not reply to broadcast messages so as to avoid collisions with each other.

Can you tell if an implementation of broadcast messages is planned?