RE: 8kernal/8modules for c64-II ? OR-Gate with diodes

From: Scott McDonnell (netsamurai_at_comcast.net)
Date: 2007-04-12 15:54:03

OR gate from diodes:

A ------>|---|-----> out
             |
B ------>|---|
             |
             / Resistor for voltage drop (1K?)
             \
             /
             |
             |
            \/ Ground

Hopefully that stays lined up

Scott McDonnell
          



> -----Original Message-----
> From: owner-cbm-hackers@ling.gu.se 
> [mailto:owner-cbm-hackers@ling.gu.se] On Behalf Of 
> Antitrack@networld.at
> Sent: Thursday, April 12, 2007 9:10 AM
> To: cbm-hackers@ling.gu.se
> Subject: RE: 8kernal/8modules for c64-II ? OR-Gate with diodes
> 
> 
> 
> Zitat von ruud.baltissen@abp.nl:
> 
> > Hallo ATT,
> > 
> > 
> > > Okay. Let me think about this again, Ruud:
> > > IF A13=1 then Memorywanted=somewhere between e000-ffff 
> (KernalROM) 
> > > ELSEIF A13=0 then Memorywanted=somewhere between a000-bfff
> > > (BasicROM) ?
> > 
> > Yep.
> > 
> >  
> > > So if A13=0 then I must Chipselect. This is not an OR gate,
> > > it is an AND gate, isn't it?
> > 
> > No. Write down the 0/1-tables for both and you'll see that you need 
> > the OR gate.
> 
> You are right, it is an OR gate that I need.
> Basically, I'll take the A13 line coming out of the kernal 
> socket, and OR it together with the Chipselect-Line which 
> also comes from the kernal socket, and I feed the result of 
> the OR-gate into the 
> STROBE-line of the 74LS157. So the resulting three A15, A14, 
> and A13 lines for the 27c1001 eprom will all be at 0. A16 
> will be 1, because A16 is 
> connected to the Chipselect-Line from Pin11 of the module port. 
> 
> Now, some old electrician friend told me that I can use 
> diodes (1N1418, 
> is this the right diode to be used ?) to substitute for an OR 
> gate, but I 
> cannot remember in what direction the diode must be placed...any hint?
> 
> Yours
> ATT
> 
> 
> --------------------------------------
> Ein Service von http://www.networld.at
> 
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