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NNTP-Posting-Date: Tue, 19 Nov 2002 16:43:58 -0600
From: "David Jones"
References: <7UjB9.9017$N02.firstname.lastname@example.org> <email@example.com>
Subject: Re: I need an 8 to 256 decoder or equivalent
Date: Tue, 19 Nov 2002 17:32:01 -0500
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sorry I didn't understand what you meant the first time but that's exactly
the sort of thing I need. I have to sit down with paper and pencil and
figure out how the mechanics work but I like the idea.
wrote in message
> Michael F. Coyle wrote:
> > "David Jones" wrote in message
> > news:vwCdnTLqxccMX0igXTWcrg@comcast.com...
> >> I'm trying to use an 8 bit binary input to select 1 of 256 different
> >> LEDS(I'm using leds as an example). I know there exists a 4bit input 16
> > bit
> >> output decoder but I don't know how to get 256 options using it with
> >> IC's. How do I make the equivalent of an 8 to 256 decoder with the
> >> discete components? any suggestions are welcome.
> >> thanks
> >> david
> > You would need seventeen 74xx154's. First, wire the bottom 4 address
> > (let's call them ADDR3 thru ADDR0) to the '154's address inputs A3-A0.
> For LEDs it can be done with just two 4-> 16 line decoders, one with
> high outputs and one with active low outputs.
> One chip is driven by D0-D3 and has 16 current limit resistors in series
> its outputs each feeding the rows of a 16X16 matrix of LEDs.
> The second chip is driven from D4-D7 and feeds the colums of the matrix.
> Obviously the viability of this for your application depends upon the load
> resembling a diode.....
> Regards, Dan.
> ** The email address *IS* valid, do NOT remove the spamblock
> And on the evening of the first day the lord said...........
> .... LX 1, GO!; and there was light.
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