3B1 Unix PC emulator -- keyboard driver (half) done

Hi guys, I've just finished adding a rudimentary keyboard handler to my 3B1 emulator (http://www.philpem.me.uk/code/3b1emu). Problem is... it doesn't quite work. I can get into the test software, and if I hit a key it'll drop into the main menu. Problem is, when I get to the main menu, it doesn't seem to recognise the commands I'm entering. That is, I can enter a menu item number (e.g. 6 <CR> for Goto Subsystem Menu), it echoes to screen correctly, but then the screen clears and I'm thrown unceremoniously back to the main menu, instead of getting passed along to the subsystem menu... This happens with all the possible menu selections, and the "expert mode" command ("s4test"). Is anyone aware of any quirks with the test software which might cause this type of behaviour? Does anyone happen to have a 3B1 and an RS232 protocol analyser (or a logic analyser with RS232 decoding)? It'd be really handy to have some dumps of the data sent and received by the 6850 ACIA (the keyboard comms controller chip) when the keyboard is initialised, and when various keys are pressed... (If I had a 3B1 of my own, it'd be on the table downstairs with a keyboard sniffer cable and my HP logic analyser mainframe plugged in...) Thanks, -- Phil. classiccmp at philpem.me.uk http://www.philpem.me.uk/