VDUFFD0 Jumper - nealcrook/multicomp6809 GitHub Wiki

On the V110 PCB, there is a jumper labelled VDUFFD0 which connects to pin 48 on the FPGA. This input pin has an internal pullup so that it defaults to 1. Fitting the jumper pulls the input to 0.

This jumper affects the I/O decode of the serial ports:

Jumper	UART0 (PS2/VGA video terminal)	UART1 (SerialA)
OFF:	$FFD0-$FFD1	$FFD2-$FFD3
ON :	$FFD2-$FFD3	$FFD0-$FFD1

All of the software uses $FFD0-$FFD1 for its primary I/O. Therefore, if you are running with the PS2/VGA video terminal you should have the jumper OFF. If you are connecting to a terminal or terminal emulator on the SerialA port, you should have the jumper ON.