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NNTP-Posting-Date: Mon, 18 Nov 2002 00:08:43 -0600
Date: Mon, 18 Nov 2002 00:10:11 -0600
From: gary drummond
X-Mailer: Mozilla 4.78 [en] (Win98; U)
Subject: Re: I need an 8 to 256 decoder or equivalent
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Si Ballenger wrote:
> On Sat, 16 Nov 2002 15:01:02 -0000, "markp"
> >"Gibbo" wrote in message
> >> "David Jones" wrote:
> >> >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
> >> >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 least
> >> >discete components? any suggestions are welcome.
> >> >thanks
> >> >david
> >> >
> >> That's going to be big and unweidly.
> >> Instead think multiplexing and 16 X 16 array for the leds.Your component
> >> will drop substantially.
> >Yep, use a PLD with 8 inputs and 32 outputs and wire the LEDs as a 16x16
> >matrix. Alternatively, use a pair of 4 to 16 decoders, an inverting buffer
> >and a non-inverting buffer, and wire the LEDs as a matrix. Your 'example' of
> >LEDs is a good one because these are diodes, and you need them for
> I'm looking for something similar to attach to a universal IR
> remote control. The remote has a chip that has 12 pins that input
> the button pushes. There are only 32 buttons on the chip, but the
> matrix scheme appears to be 12x12, as the chip pins are connected
> 2 at a time in various combinations via the button pushes. Is
> there a multiplex chip available that could take the 8 pins from
> the parallel port and use them to multiplex the 12 pins on the
> remote to duplcate the button pushes? Below is where I used two
> of the IR chip pins to do a "channel up" button push. Would be
> neat to do all 32 button pushes. thanks.
A crosspoint switch (8x8) can be wired to the 12 pins and be
directed to connect any of 6 pins to any of the the other
Steve Ciarcia wrote an article about an audio/video switch in
Feb 1986 Byte Mag. I think he has done another one in his
Circuit Cellar mag. You should get the theory and practical
info from one of them. http://www.circuitcellar.com/
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