I'm using Fieldserver Gategay FS-X40 to convert Modbus+ to Modbus RTU over RS-485(the only available from CSC) and I can read but not write.

Any clue?

My friend told me to apply the 15-30-50 law:
Drop the CSC from 15 cms, and see if works, if not, drop it from 30 and try again, if doesn't work, from 50 and as a last resource, change it.

Since I want to get through this, I ask you for help.

Thanks in advance.

 

Sorry, I really have no idea what you are saying.

However, if reads work and writes do not, that often is a master timeout problem. Since many small devices update parameter changes to nonvolitale memory, the write can take much longer than a read. In fact, if the RTU device is a multi-processor system even reading different data can take different amounts of time. For example, I worked with a truck-loading batch-loader where the digital I/O was on the "comm card" and digital data responses started within 30-40msec; analog data was on a second CPU and would take 200-300msec to start a response; all writes would take from 600-800 msec due to NVRAM update on the main CPU board (yet another card).

Since your master sees your slave as MB+ (ie: a fast slave on a 1-meg bits per second network) it could be expecting a response in say 50-100 msec. It doesn't understand that the gateway is bridging this speedy message to a pokey serial line.

best regards - LynnL, www.digi.com