[Techtoolslist] Asteroids 9010 script

[Martin White]

Hi All,

I¹ve been looking at the Asteroids script that¹s on the TT FTP lately and am
a bit puzzled as to why part of it won¹t work!

I¹m talking about the one that has tests for RAM, ROM, draws the cross on
the screen, triggers the sounds and checks the address decoding using the
probe.

It¹s this last test that I seem to have a problem with!

I¹ve done it on a sick board and all the chip selects check out perfectly
except for the one for PROM2 (L3-7). This one always reads 0 on the probe.
Just to be sure I¹ve tried the same on a working board but I get the same
thing.

Now thing is, I¹ve gone over the schematics and checked the pin numbers and
memory addresses, together with checking over the script and I can¹t really
see much of a reason why just this one would not read correctly when all the
others do.

Before I scratch my head much more, as this script has been out there for
over 4 years now has anyone else resolved this? I must be missing some very
obvious point I guess?


>From what I can make out the script just reads from the given address 64

times and with the probe set to sync to the address cycle counts the number
of times the chip select is pulsed (or goes low rather). It then takes the
result from the probe tip, AND¹s it with 7F and sees if the probe registered
all 64 hits. I think :o)

Anyone explain what¹s going on?

Ta,
Martin.
-- 
Guddler's Domain
http://www.guddler.co.uk

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://seven.pairlist.net/pipermail/techtoolslist/attachments/20060527/11537bdc/attachment.htm>