RE: iec to pet

Dia... Freeware go to http://live.gnome.org/Dia Much better than drawing :) 

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Steve Gray
Sent: Friday, October 01, 2010 7:59 PM
To: cbm-hackers@musoftware.de
Subject: Re: iec to pet

Ok, looks like I'll have to re-check the board. Perhaps I missed something,
like 
a trace under a chip. I do know that the board works fine.
Thanks for the feedback.

Steve

PS:Can anyone recommend a good free schematic editor? I think I played with 
Eagle a few years back, but perhaps something new is out now.



----- Original Message ----
> From: "Hoffmann-Vetter, Martin" <martinhv@arcor.de>
> To: cbm-hackers@musoftware.de
> Sent: Fri, October 1, 2010 6:25:37 PM
> Subject: RE: iec to pet
> 
> Hello,
> 
> > To me, it looks like /WE and /OE will be active together, not usually
> > a good thing.
> 
> Yes, i think there is an error, too!
> 
> Because:
> 
> /OE = /(SR/W & SPhi2)
> 
> That is correct!
> And:
> 
> /WE = /(SPhi2 & /(/OE & /0))
>     = /(SPhi2 & OE)
>     = /(SPhi2 & SR/W & SPhi2)
>     = /(SPhi2 & SR/W)
>     = /OE
> 
> That isn't correct! I Think the logic without U4b is better. Then the
output
> from U4d must be short to the input from U4c. So the logik is:
> 
> /WE = /(SPhi2 & /OE)
>     = /(SPhi2 & /(SR/W & Phi2))
>     = /(SPhi2 & (/SR/W | /Phi2))
>     = /(SPhi2 & /SR/W | SPhi2 & /SPhi2)
>     = /(SPhi2 & /SR/W | 0)
>     = /(SPhi2 & /SR/W)
> 
> And that must be okay!
> 
> Greetings from Germany
> 
> Martin
> 
> 
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> 


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