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Paul Keizer

Programming plc through profibus

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Hello, I started already a topic before about this, but because it was a long time ago i thought i repost it. My problem is that i can't connect to the plc through profibus. I already tried the steps as described below, but i can't get it running. Any body know what i'm doing wrong?

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Hi, The USB-MPI adapter requires 24v to power up. When connecting directly to the processor the PLC supplys this voltage. when connecting to profibus the 24v pins are not used. its been a few years since ive used a seimens plc but we used breakout boards and added a 24v power supply to power up the adapter. i dont remember what the pins were. sorry Delbert

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I am guessing it is a 315-2DP CPU since it has both MPI and DP ports. For a 315-2DP, you have to enable the Profibus port in the HW Configuration, and download this initial Configuration via MPI. A factory fresh 315-2DP cannot be configured via the DP port since it is disabled. Maybe this is the cause of your problem. edit: But if you connect to the Profibus port on the CPU, and the power leds on the adapter do not light up, then it seems to indicate the DP port on the CPU is defective. Edited by JesperMP

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Hi Did you ever get this sorted out as I am Having the same problem?

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This is a good post and a must try. Ill definitely try this when i got home as im out of the country now. I think Profibus is connected to pins 3 and 8 only so it really makes sense that it is not supplying the pc adapter when you connect it ( just a wild guess ). I hope someone will shed a light on this. :)

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