There is currently an ACIA emulator which uses the ANSI Display and PS/2 keyboard connection. Adding a second ACIA port which will use I/O pins as a serial port. An FTDI can be attached to these pins which will allow access from a Computer USB port. This is easier for screen capture and uploading of S-Record files.

Using Neal Crook's "Buffered UART" VHDL code which has improvements compared with Grant's ACIA code but it has a small difference since it uses Serial Clock Enables.

Locating the new serial port at addresses $8028-$8029.

Adding a serial port select jumper using one of the J3 jumper blocks on the RETRO-EP4CE15 card. If the jumper is left out the VDU and PS/2 are used for I/O. If the jumper is installed the new serial port is used for I/O. This is done by swapping the memory decode addresses.

Tested and works.