Date   : Fri, 22 Feb 2008 13:28:48 +1100
From   : msmcdoug@... (Mark McDougall)
Subject: BBC FPGA Boots to BASIC... almost...

Jonathan Graham Harston wrote:

> Snap! http://mdfs.net/Software/PDP11/BBCBasic/blog/img06.gif
> Bruuhahahahaaahh!!!

Nice!

> If ROM paging wasn't working, that may cause a problem, but it
> would before it gets back to BASIC to REPORT the error. Also, you
> would be likely to see the problem on BREAK/RESET when the ROMs
> are initially walks through to initialise them.

It should be working in all cases, but it's something for me to check again.

> Does the problem happen with all errors, or just Mistake? Try:
> PRINT FRED
> to generate "No such variable" and see what happens.

Same thing - I see "N" and it freezes...

> Does the problem happen with all printout, or just printout after
> an error occurs? Try:
> REPEAT PRINT "HELLO":UNTIL FALSE
> This should continuously print HELLO

Yup, no problem with it. I ran a "hello world" program a few days ago and 
left it running for a couple of hours.

> Is the printer buffer filling, or is it something else? Try
> selecting the printer sink with:
> *FX5,0
> and then generate the Mistake error again.

Same deal.

> If you have a way of monitoring the LED state,
> that would tell you if printer output is being inadvertantly
> selected and the buffer is filling up.

Not atm... the board I'm using atm only has 1 LED and that's used for 
something else... :(

I should mention that pressing <ESC> also hangs the machine. From the BASIC 
prompt I see "Esc" before it hangs...

The other weird thing is that I have a hot-key sequence that is supposed to 
reset the design - resets the CPU and all the registers in the design - but 
that results in a clear screen and a hang without anything displayed on the 
screen. I have no idea why this doesn't restart properly. It may be 
related... I have more investigation to do when I get the chance, which I 
haven't for a few days now...

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"