I have been working on creating a UART on an FPGA. I can successfully transmit and receive single characters typed on PuTTY. However, when I set my FPGA to constantly write a large sequences of "A", sometimes I end up with a sequences of "@" or some other characters until I reset the FPGA a few times.

I believe the UART on the computer looses track of the difference between the start bit and a zero. The delay between the two "A" is ~ 30us (measured with a logic analyzer) and the baud rate is 115200 8N1.

Is there a minimum delay that must be maintained between two consecutive RS232 frames?