I am using CP 341-1CH01-0AE0 (RS 485) master & trying to communicate using a modbus simulator with the PC as slave via RS 485 to RS 232 converter to COM port 1 of the PC. modbus parameters to both the CP 341, the simulator & the PC COM port has been set to 19200 kbps, 8 data bits, 1 stop bit, parity none, slave address 1, & the start address are similar to both. the master is sending a request to the slave using a function code 3. the CP 341 is showing "TxD & RxD" as normal & the modbus simulator is also showing normal with the "RS" keeps flashing on the screens as the master "TxD & RxD" led continuosly blinking on the CP341. Our problem is no data being receive by the master after forcing some values in the define start address the send done bit is is not coming at all. the PLC code is showing an error "0E62H" in the send block. the manual says "Reply message with excepyion code 02 : illegal data address. See Manual of slave device. we have try changing the define data start address but problem exist. Please advice.

Thanks & best regards,

Mumtaz

good news first: You are getting a message back from the Modbus Slave so your modbus coms are working in general.

Bad news (as you know), you are getting an exception message back as the Modbus Slave device is NOT capeable of serving the PLC's (Modbus Master) request.
The message 0E62hex is what the manual says it is and what you worked out already, there is not much more you can do from thePLC's point of view.

Having said that, bear in mind that requesting address 520 together with Modbus Function code 3 (Read multiple holding registers) equates to a "real" Modbus address inside the Modbus Slave of register 40521 (the silly old Modbus n-1 based addressing rule applies).
I don't know how your Modbus PC based Simulator "handles" Holding Registers and/or how you "declare" them for testing, but you may want to try to setup 40xxx ones and see if it helps.

I hope this helps