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I think your error is self explanitory.
You cannot write to an input port. You need to make it an output.
Also, outputs cannot be read internally. Either make it a buffer (like it suggests) or use an internal signal.
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" I have tried to run the above code but and they are executing successfully , the problem that is not that how do I assign the pins, auto assigning the pin gives a wrong output and when using the DE1 pin assignment how do i change the name as there is discrepancy in naming system "
https://www.alteraforum.com/forum/attachment.php?attachmentid=6640