Host Engineering Forum
General Category => DirectSOFT => Topic started by: Liviu on April 07, 2010, 09:32:11 PM
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Which kind of protocol need to use to programming stations with individual binary adress,for example 50 stations,connections in paralel with length of cable 5 meters between stations
One station include 4 inputs and 7 outputs ,leds,buttons etc
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I don't believe that the programming package can work over RS485. I think only Modbus is usable by that and it's only for data gathering. You will have to connect individually to the program ports or install Ethernet modules and switches to connect them all.
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Are you sure you can't use 485 for programming, Bernie? I believe DSLaunch allows you to specify node addresses when creating a DirectSoft comm link, and I can't imagine why they would do that unless DirectSoft could be used in a multi-drop topology. Maybe the PLC's don't support programming over the 485 and you have to have a 485-232 converter at each PLC. I'm even a little skeptical of that theory, because I think in a lot of the PLC's, it's just 485 and 232 connections to the same comm channel, so obviously if you could program over the 232 version of the port, the 485 connection shouldn't mind.
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I was basing this on K-Sequence and Directnet can't be used as protocols going OUT of the PLC on RS485. I could be wrong about the programming though.
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DirectNet can definitely be multi-dropped, although I think it uses RS422, not RS485. My very first programming task at TI, about 122 years ago, was to write some networking tools for DirectNet. I have since forgotten everything I knew about it, but it definitely can be done.
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I haven't written a communication package but it doesn't take much to realize that you can't take communication programming that allows for simultaneous send/receive operation (RS232, RS422 - 4 wire) and connect it up to a one way at a time (RS-485) connection. For one thing it is going to get its own transmission back into the receive port. It has to ignore that (or possibly use it as a collision indicator) and factor in turn-around times. All I mentioned is I don't think the protocol used by DirectSoft when going through the serial port can use RS-485. Does someone know otherwise?