I am looking for help with a seemingly simple matter. A device I am trying to communicate with is expecting a modbus address request of 40686, for example. Using the ibox ECRX, the request is transmitted as Function Code 3 with an address of 686. The slave device chokes and says "illegal data address". I used port mirroring and Wireshark to intercept the error and attached the screenshots, not sure if they will make it to this post.
Is there any way to transmit the full register address of 40686 to the slave device? I think this is my problem. If I use ModbusPoll and read 40686 I get a proper response. If I try to read 686, it's illegal.
Thanks,
Murray