framing error in uart
Stuart,
Do you have a RS232 translator chip between the FPGA and the PC? While you can sometimes eliminate these chips on short cable runs, you have to remember to an an extra inversion in the input and output. If you did not use a translator and have not added another inversion, then that could be the source of your framing error. Please note that you have to invert the IO pins. A common mistake is to just try and invert the data. Just inverting the data will not invert the start and stop bits, so it will still fail.
If you are still getting framing errors, then try adding a delay between transmissions. If you are transmitting a continuous string, and the PC started listening in the middle, it will not be able to find a good start of a character.
You can also start your terminal program first. Then flush its buffer and finally last start up the FPGA. For a good freeware terminal program that allows easy buffer flushing, look for TerraTerm.
---- Steve
P.S. You have double and triple checked all the baud rate settings, right? The wrong baud rate can give that problem. To verify that the FPGA is sending at the proper baud rate, transmit 0x55 or 0xAA and measure the pulse widths with a scope.