HEX 
104 F10 !  ( select 9600 baud in Baud register )
000C F11 ! ( enable transmit and receive circuits via Control register )
F12 @ U.   ( read and display the status register, 
           ( if high bit set, ok to send. You must always read the status 
           ( register before transmitting )
41 F13 !   ( send the letter ‘A’ out the data register )

           ( To receive a character, I used this:
F12 @ U.   ( read status, if bit 13 set, there is a character in the receive buffer. 
           ( You must always read the status register before reading the data )
F13 @ U.   ( read and display the character value )

           ( Error flags are in bits 9-12 of the Status register. 
           ( To clear these bits, do the following:
0F00 F12 ! ( write a bit to each flag to be cleared )
0 F12 !    ( write a zero to the status register )
F12 @ U.   ( notice that bits 9-12 are now clear )