Minimig Shared RS232

By wiring the MCU (PIC18) and the fpga via an AND gate one can eliminate the jumper currently present on the rs232 TxD.

RS-232:
Default voltage level is negative (-3 .. -25) = Logical "1"

Truth table: 00 0 01 0 10 0 11 1

http://en.wikipedia.org/wiki/Rs232#Voltage_levels
http://www.winpicprog.co.uk/pic_tutorial7.htm