Simulate modbus master to Siemens CP341 Slave

Hi all,
Does anyone have any experience trying to simulate a Modbus master using a PC, The PLC is a cpu 300 with a CP341 RS485. I am waiting on parts but would like to simulate inputs to the plc using the Modbus communication to the cp341. Is it possible to do this from a PC I know there is modbus32 software but how can you connect your PC to the PLC?
Thx

http://www.plctalk.net/qanda/showthread.php?t=78209

This thread may help you out.

Regards,

All of the those generic Modbus master will write one or more values to a slave, but frankly, if it were me, I'd buy the I/O cards, force the inputs and be done with it. The task of getting Modbus to work on Siemens is more than a project, it's brute labor.

I read about the issues users have trying to get Modbus working on Siemens controllers and just figuring out which CPU needs which firmware update and which Modbus option to talk to which port and with which dongle or no dongle even before one gets to the somewhat arcane programming/configuration is eye-opening.

Between us fellas, I suspect that the German company that was paid to develop and promote Profibus considers it a bother that the marketplace insists that their controls even deal with the Modbus as a comm protocol. Their ability to obfuscate (to confuse, bewilder, stupefy or make unclear) their implementations of Modbus reflects that attitutude.

Go ahead and try it if you value your time at nothing.

I say this as a Modbus guy who helps on Modbus issues when I can, but I can't help Siemens victims, they're on their own.

Wow. You must be a competitor.

If the CP341 doesn't support the Modbus RTU protocol I would stay away.
Ditto what danw said. If maico has to build the packet headers, fuss with character timing and do the checksums or CRC checks he will be pulling his hair out by the time he is done and wished he listened to danw.

I have a 16 input and output manual card to simulate inputs and outputs. When the S& turns on a bit I see a light on the card. There are 16 little ( fragile ) toggle switches on the card for simulating inputs. The only draw back is that I had to flip the switches as I responded to lights. My responses were relatively slow but then I didn't have to write a simulation program or go through any the wiring and communication hassles.

Perhaps JRW know about this card.

I tried the exact thing - CP341 to multiple modbus devices, in the end I gave up and put a dedicated modbus server in between and communicated to the S7 by ethernet.

If you want to communicate to ONE modbus device it was ok, but more than one device and I couldn't get it to work. The only way I ever got it speaking to multiple devices was by putting the PLC into STOP then RUN between each one! Not really a practical solution!

From memory it was something to do with one of the parameters of the block wouldn't initialise when the PLC was in run mode. By the time I got to this point I was so done with it that I just threw the CP away!

If you do persist with it I have a few notes and screenshots of my settings if you PM me I will share them.