Modbus TCP comms between Eurotherm controllers and GE IC695ETM001 module (RX3I)

I am trying to get a few data points from three different Eurotherm controllers (PV and setpoints) into a GE rx3i system with a CPU315 plc along with an ETM001 module. I know the controllers and the ETM module can talk over Modbus TCP. First question is what is best way to set up comms, is it better to have the rx3i system be the master and request data from the three controllers round robin or is it better to have the controllers be masters and have the rx3i system be the slave? I read making the rx3i be the master requires more programming (like COMM_REQ instructions). Can the setup even be done having the plc be the slave to all three controllers at the same time? One other question is outside of the manual does anyone know where to locate example code on how to read in data on the plc side?
Standalone, single loop PID controllers like Eurotherm usually function as a Modbus/TCP server (slave) only.

There’s nothing that prevents a PID controller from being a Modbus client if the manufacturer provides the firmware for such; such is just not common.

You need to confirm that the particular Eurotherm model you have can actually function as a Modbus/TCP client.
> I read making the rx3i be the master requires more programming (like COMM_REQ

Programming a Modbus Master/Client is usually more work than dealing with a Modbus server/slave.

A client/master always needs to issue the polls/commands and needs the programming to handle multiple server/slaves. And it needs to deal with data returned to it.

On the other hand, commercial devices like the Eurotherm have their server/slave register tables established and documented by the manufacturer, so the only Modbus ’programming’ task is communications setup: IP address; subnet mask; gateway IP.

PLC server/slaves do need to have the slave registers configured and populated with data.