Dear Sirs
I am trrying to communicate two PLC`s (slave-master configuration) via radio modems using RS485 ports. Using ?native? protocol I can communicate both PLC?s. However, using modbus RTU or ASCII I am not able to communicate them.
I performed another test in which a PC reads information from a ?remote ? PLC via radio modems connected to their RS232 ports ,and it works fine.
I think this problem has to do with timing. Is there any way in which master PLC allows more time to receive response from slave PLC when using Modbus ASCII/RTU?
On the other hand, I have a PLC with a Xserver attached to it and I am able to send information to a fixed IP address PC running Webserver. It works fine when Xserver is connected to my LAN which is connected to Internet via a DSL provider. I recently installed a satellite internet service equipment (for remote telemetry applications) and I am not able to transmit information using PLC+Xserver. I talked to ISP and he assured that all TCP/IP ports are enabled and open. When I connect a PC to the modem (satellite internet) I am able to access websites, send emails and doing ftp at a very reasonable speed.
Do you have any idea of what the problem might be and how can be solved?
Your help will be greatly appreciated,
Sincerely,
Jes?s Baez