Magelis Modbus RTU comms

Hello,
I am wanting to get a Magelis to read holding registers from an IO device using FC04, but in testing it always seems to use FC03.
The manual says FC04 is a supplementary address, yet I need to use it.

I don't think the IO device supports FC03 for input registers, the example only shows output image for FC03.

I have used this IO type with a PLC using FC04 and m is it works, I just wanted to copy the same config.
For reference, I can set outputs from the Magelis using the same config as the PLC so know this is correct.

Any suggestions on how to use FC04, or to force it to read using this function?

Not sure, but a couple of things to check
if iec addressing mode is selected use addresses in the format %IW123 (dont remember seeing this option)
if iec mode is not selected use addresses in the format 30123

GeoffC said:

Not sure, but a couple of things to check
if iec addressing mode is selected use addresses in the format %IW123 (dont remember seeing this option)
if iec mode is not selected use addresses in the format 30123

Click to expand...

Thanks Geoff, the IEC mode is only for Modbus/TCP, not RTU. I have tried both types of addressing 3xxxx & 4xxxx, but both seem to use FC03.

I have double checked the manual for the Remote IO, & there implementation of FC03 only supports reading of Output registers.

Geoff,
oops, the IEC mode is also available for RTU mode, I just overlooked where it was
Local support have advised of a solution that I am yet to test, I am hoping to do so later in week.
Interesting enough, when using Kingfisher Telemetry equipment, an address is only entered, so it uses FC04 by default as it always requires to read Input registers rather than holding registers.