Groups > sci.electronics.design > #518783

Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL

From	"tom" <tmiller11147@verizon.net>
Newsgroups	sci.electronics.design
Subject	Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL
Date	2018-10-09 00:15 -0400
Organization	A noiseless patient Spider
Message-ID	<pph9tk$9rl$1@dont-email.me> (permalink)
References	<FpWdnYuq0ujJaSbGnZ2dnUU7-I_NnZ2d@giganews.com>

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"John Robertson" <spam@flippers.com> wrote in message 
news:FpWdnYuq0ujJaSbGnZ2dnUU7-I_NnZ2d@giganews.com...
>I am looking for a way to take the TTL level outputs (treating them as 
>inputs) of a 7448 and convert them back to the original BCD TTL input 
>levels (but as outputs) and I figured a simple socketed GAL would do the 
>trick for the least cost. However I don't have the skill set to build the 
>GAL logic table for this. Any suggestions? And no, I can't simply remove 
>the 7448 from the circuit.
>
> Go easy on me here, I can unscrew hardware, but Boolean has never been my 
> forte...
>
> Thanks!
>
> John :-#)#
> -- 

One way to do it is to use an EPROM.  Connect the seven segments to AD0 to 
AD6. Use the first four data outputs (D0 to D3) for the BCD code. Make up a 
table with the correct memory locations to put 1s in for the decoder. Tie 
/CE and /CS to the appropriate levels. A 2716 would work fine, just ignore 
the unwanted outputs and tie AD7 to ground.


Regards

Thread

Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-08 17:20 -0700
  Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jeff Liebermann <jeffl@cruzio.com> - 2018-10-08 18:57 -0700
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-08 19:08 -0700
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-08 19:13 -0700
      Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-08 19:27 -0700
        Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jeff Liebermann <jeffl@cruzio.com> - 2018-10-08 21:06 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jeff Liebermann <jeffl@cruzio.com> - 2018-10-08 21:36 -0700
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL gnuarm.deletethisbit@gmail.com - 2018-10-08 20:27 -0700
      Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-08 21:19 -0700
        Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jeff Liebermann <jeffl@cruzio.com> - 2018-10-08 21:40 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 00:20 -0700
            Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL gnuarm.deletethisbit@gmail.com - 2018-10-10 15:43 -0700
              Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-10 18:46 -0700
        Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL gnuarm.deletethisbit@gmail.com - 2018-10-08 22:11 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 00:27 -0700
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Rob <nomail@example.com> - 2018-10-09 17:08 +0000
  Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL "tom" <tmiller11147@verizon.net> - 2018-10-09 00:15 -0400
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 00:26 -0700
      Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-09 14:23 +0200
        Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL jrwalliker@gmail.com - 2018-10-09 06:43 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 08:41 -0700
            Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL dplatt@coop.radagast.org (Dave Platt) - 2018-10-09 10:50 -0700
      Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jeff Liebermann <jeffl@cruzio.com> - 2018-10-09 09:15 -0700
        Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 10:01 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-10-09 21:01 +0300
            Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 11:13 -0700
              Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL bitrex <user@example.net> - 2018-10-09 18:35 -0400
                Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL TTman <kraken.sankey@gmail.com> - 2018-10-09 23:43 +0100
                Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL bitrex <user@example.net> - 2018-10-09 19:49 -0400
                Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL bitrex <user@example.net> - 2018-10-09 19:50 -0400
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jeff Liebermann <jeffl@cruzio.com> - 2018-10-09 17:25 -0700
            Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 19:15 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL gnuarm.deletethisbit@gmail.com - 2018-10-10 16:46 -0700
            Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-11 02:08 +0200
              Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL gnuarm.deletethisbit@gmail.com - 2018-10-10 18:37 -0700
                Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Gerhard Hoffmann <ghf@hoffmann-hochfrequenz.de> - 2018-10-11 13:35 +0200
      Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL gnuarm.deletethisbit@gmail.com - 2018-10-10 15:45 -0700
        Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-10 18:50 -0700
          Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL Jasen Betts <jasen@xnet.co.nz> - 2018-10-11 05:39 +0000
  Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL bitrex <user@example.net> - 2018-10-09 02:18 -0400
  Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL TTman <kraken.sankey@gmail.com> - 2018-10-09 17:51 +0100
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL bitrex <user@example.net> - 2018-10-09 17:38 -0400
  Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Larkin <jjlarkin@highland_snip_technology.com> - 2018-10-09 17:52 -0700
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL John Robertson <spam@flippers.com> - 2018-10-09 19:16 -0700
    Re: Need to construct the logical reverse of a 7448 - perhaps using a GAL bitrex <user@example.net> - 2018-10-09 22:48 -0400

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