1 pointHere is the problem - you take the signal from the button connected to pin C4 and use that as a clock for the ledst0 flip-flop. This is not how you use an FPGA. Pin C4 is not a clock input pin, which cause the error 1108 you see, and logic signals like btnl should not be used as a clock. FPGAs are intended to be used for synchronous logic designs where a large number of flip-flops are clocked with a common clock. In order to make this possible the clock is distributed to all the flip-flops in this clock domain using special clock buffers and clock networks. The source of the clock is typically coming from an input pin on the FPGA and only a select few pins can be used as clock input. The input clock can be used as is or can be feed to a clock management tile that has resources like PLLs and DCMs that allow you to create a clock with different clock frequency. The Nexys3 board has a 100 MHz clock input signal connected to pin V10 that can be used as system clock. This is what the Nexys3 manual states: Try this code instead: .ucf file: BTW, your switch might "bounce", so you might have to de-bounce the signal from the switch. See What is debouncing? Magnus
0 pointsI recently was using my Papilio One and was erasing the spi flash using the papilio loader, when it disconnected and now it doesn’t show up when I try to upload a program. I tried reinstalling the drivers, but that didn’t work. I also installed the papilio loader on a different computer, and it as well didn’t see the board. The board, with the program that was already there, works fine, but I cannot upload anything new to it, since the computer can’t see the board.