Date   : Mon, 18 Feb 2008 07:53:33 +1100
From   : richard@... (Richard Wilson)
Subject: BBC FPGA Boots to BASIC... almost...

 

> -----Original Message-----
> From: 
> bbc-micro-bounces+richard=tassiecars.com.au@...
>  
> [mailto:bbc-micro-bounces+richard=tassiecars.com.au@...
> d9.co.uk] On Behalf Of Jonathan Graham Harston
>  
> Testing on real hardware shows all unused I/O addresses 
> return &FE, not just those at &FExx:
>  
>  
> One thing to look out for is that the BBCs return &FE and the 
> Masters return &FF on unused ports. Some software depends on 
> b7 being 1 when hardware is absent (eg detecting Tube or hard 
> drive hardware).

Interesting. Do all Model Bs return &FE? What is driving D0 low as I can't
see anything obvious in the schematic.

Richard