Re: ROMs replacement

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Tue, 18 Sep 2012 20:54:40 +0200 Message-ID: <5058C370.5030106@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 09/18/2012 08:04 PM, Jim Brain wrote:
> I think a solution with all 2 input NAND gates is available as well, but
> that is getting overly academic.  It basically boils down to how much
> the OP wants to solder.

The thing is, if you look at the pinout of the '00 and the '11, you can 
save a lot of wiring by arranging the gates right and do some direct
pin2pin connections:

Multiplexer in '00 ( '+' = connect)

  1 + 12  = _Select1
  2       = Input 2
  3 + 4
  5 + 8
  6       = Output
  7       = GND
  9       = Input 1
  10 + 11
  13 + 14 = Vcc


Bank Selector in '11 :

      1   = JP301 + Pullup against Vcc.
  2 + 3   = _BASIC
      4   = _CHAR-ROM
      5   = _KERNAL and JP301 other side
      6   = _CS for EPROM
      7   = GND
     12   = A13 for EPROM
  13 + 14 = Vcc

(And to use up the unsued gate, just connect 12 + 11 + 10 + 9)

  Gerrit


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