RE: 8kernal/8modules for c64-II ? OR-Gate with diodes
Date: 2007-04-12 15:09:58

Zitat von

> 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?


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