In ID 11859930 'S7-200 Micro-PLC Optional Software Packages' is the above Library for the S7-200 with the ordernumbers. The PPI port of the S7-200 = RS485 and may directly used for the Modbus communication. MODBUS Communication With S7-200 - Download as PDF File (.pdf), Text File. The example concerns the MODBUS function code 6 (Write to slave-holding. Micro/WIN MOBDUS library is available in the S7-200 system manual ( Entry ID.

We are using a Siemens S7-200 PLC for trip handling. We want to connect this PLC to a DeltaV system using Modbus communication. We used the Siemens Modbus library to implement the Modbus function in the PLC. We now want to use the Siemens PC/PPI cable to connect it to a DeltaV serial card with Modbus protocol. We can't get it running. We now first try to use a Modbus scanner directly from a PC to test the communication.

Does anyone have some more information about the S7-200 Modbus communication? Do you have the communications specs for the S7? The setup for comms on the DeltaV serial card is drop dead easy. I've used it for many different PLC's, controllers, xmitters, etc.

Some things to look for: - Is the S7 wanting to be master or slave? (most likely slave) Be sure to set the DeltaV SIO card to accomodate. - do you have the proper pinout for the type of connection you're trying to make.

Remember it's different for RS-232, vs. 422/485 half duplex vs. 422/485 full duplex. Check DeltaV books online for diagrams showing the pinouts. - do you have the comm port configured properly for baud rate?

And data bits. (a good first guess if you don't have the S7 docs would be No parity, 8 data bits, and 1 stop bit. - are you polling the correct modbus address? - are you using the right framing? The DeltaV SIO card can go either ASCII or RTU but you need to tell it what the S7 needs to see. (probably RTU) - are you polling for a valid register(s) in the S7? You can set this by creating a corresponding data set in the DeltaV SIO card.

Remember to use the offset to line up with your modbus registers in the S7 and to use block reads/writes when possible to help speed. - again, check books online for all the goods on this topic, it's very thorough. You have clicked on the '?'

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