What is the "complement" to the 74LS154?

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
JerryH
Posts: 3
Joined: Fri Jan 07, 2011 9:05 am
Contact:

What is the "complement" to the 74LS154?

Post by JerryH » Fri Jan 07, 2011 9:14 am

I'd like to construct a multiplexed-demultiplexed control circuit. I've located specs easily enough on the 74LS154 (4-to-16 line decoder), but I can't seem to find what amounts to a 16-to-4 line encoder. I know about using a pair of 8-to-3's to get the equivalent function, but I'd like to know if a 16-to-4 exists.

Thank you for any help you can provide.

sghioto
Posts: 322
Joined: Wed Dec 26, 2007 5:16 pm
Location: Colorado
Contact:

Re: What is the "complement" to the 74LS154?

Post by sghioto » Fri Jan 07, 2011 9:51 am

JerryH

I don't think there is one. The closest single chip I know of is the 74147, a 10 to 4 line decimal encoder.

Steve G.

JerryH
Posts: 3
Joined: Fri Jan 07, 2011 9:05 am
Contact:

Re: What is the "complement" to the 74LS154?

Post by JerryH » Fri Jan 07, 2011 10:02 am

Thank you for the response.

After a little more digging, it seems that the '154 is primarily for memory addressing, so it's unlike the reverse of it was ever really needed.

Oh well.

Gorgon
Posts: 325
Joined: Wed May 04, 2005 1:01 am
Location: Norway
Contact:

Re: What is the "complement" to the 74LS154?

Post by Gorgon » Thu Jan 13, 2011 4:07 am

You could make the 16 to 4 decoder yourself with a eprom(or flash) with 16 address lines, like the 27(8/9)xx512. Program it for the different values and get whatever combination outputs you want. I have never heard about a 16 to 4 bit decoder or priority encoder type chip.

TOK ;)
Gorgon the Caretaker - Character in a childrens TV-show from 1968. ;)

User avatar
haklesup
Posts: 3037
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: What is the "complement" to the 74LS154?

Post by haklesup » Fri Jan 14, 2011 10:38 am

Check out the 74LS138 1 of 8 Decoder/Demux

The 74AS250 is close but I think not quite

And yes, you can make these out of all 74xx00 NAND or just about any kind of programmable logic family with a sufficient number of I/O pins.

Dean Huster
Posts: 1263
Joined: Wed Dec 05, 2001 1:01 am
Location: Harviell, MO (Poplar Bluff area)
Contact:

Re: What is the "complement" to the 74LS154?

Post by Dean Huster » Fri Jan 14, 2011 6:46 pm

Closest thing used to be the 74150, but it was not available in an "LS" version as I recall. We always paired 74154 with a 74150 for a MUX/DEMUX circuit. The '150 is a 1-of-16 multiplexer. You can easily cascade two 1-of-8 MUXs and do it in LS, but you'll need an additional inverter for the enable pin of the second MUX.
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

Post Reply

Who is online

Users browsing this forum: No registered users and 50 guests