colin@vu-vlsi.UUCP (Colin Kelley) (01/19/87)
I'm looking for a 1-of-8 decoder (like the 74138) but with active high
outputs. I've looked through several TTL data books, but I haven't been
able to find one. This isn't exactly crucial, as the same effect can be
had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs
to my design after paring the chip count down so carefully with some neat
ICs (like the 74259).
Is an active high decoder really all that uncommon, or was I just unlucky
in my selection of data books to check?
Thanks!
-Colin Kelley ..{cbmvax,pyrnj,psuvax1,bpa}!vu-vlsi!colinphil@amdcad.UUCP (Phil Ngai) (01/20/87)
In article <571@vu-vlsi.UUCP> colin@vu-vlsi.UUCP (Colin Kelley) writes: >I'm looking for a 1-of-8 decoder (like the 74138) but with active high >outputs. I've looked through several TTL data books, but I haven't been >able to find one. This isn't exactly crucial, as the same effect can be >had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs >to my design after paring the chip count down so carefully with some neat >ICs (like the 74259). Get with it, guy! Where have you been the last six or so years? Use a PAL. TTL is obsolete and dead. For high speed, PALs come in D varieties which run at about 10 nS, and that gives you a trip through an AND-OR plane. For low cost, the plastic PALs are amazingly cheap. New PALs provide buried state registers for implementing synchronous state machines. Programmable polarity outputs mean an end to DeMorganing equations. There are many new innovations such as UV erasable, EE erasable, RAM programmed (great for debugging), *large* arrays, programmable sequencers etc. All designers should have PALs as part of their collection of tools. Note: PAL is a trademark of Monolithic Memories but we make them too. -- Social security is welfare for the elderly. Phil Ngai +1 408 749 5720 UUCP: {ucbvax,decwrl,hplabs,allegra}!amdcad!phil ARPA: amdcad!phil@decwrl.dec.com
rep@genrad.UUCP (Pete Peterson) (01/20/87)
In article <571@vu-vlsi.UUCP> colin@vu-vlsi.UUCP (Colin Kelley) writes: }I'm looking for a 1-of-8 decoder (like the 74138) but with active high }outputs. I've looked through several TTL data books, but I haven't been }able to find one. This isn't exactly crucial, as the same effect can be }had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs }to my design after paring the chip count down so carefully with some neat }ICs (like the 74259). } }Is an active high decoder really all that uncommon, or was I just unlucky }in my selection of data books to check? } }Thanks! } } -Colin Kelley ..{cbmvax,pyrnj,psuvax1,bpa}!vu-vlsi!colin You already have one! Active-high decoders are not common, but the '259 (originally called the Fairchild 9334) acts as an active-high-output 1-of-8 decoder if you hold the CLEAR and ENABLE lines low. It's also available in "FAST" (74F259) if you need greater speed. pete peterson usenet: {decvax,linus,wjh12,mit-eddie,masscomp}!genrad!rep phone: (617)369-4400 x2478
daveh@cbmvax.cbm.UUCP (Dave Haynie) (01/20/87)
> Keywords: ICs > > In article <571@vu-vlsi.UUCP> colin@vu-vlsi.UUCP (Colin Kelley) writes: >>I'm looking for a 1-of-8 decoder (like the 74138) but with active high >>outputs. I've looked through several TTL data books, but I haven't been >>able to find one. This isn't exactly crucial, as the same effect can be >>had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs >>to my design after paring the chip count down so carefully with some neat >>ICs (like the 74259). > > Get with it, guy! Where have you been the last six or so years? Use a > PAL. TTL is obsolete and dead. For high speed, PALs come in D > varieties which run at about 10 nS, and that gives you a trip through > an AND-OR plane. For low cost, the plastic PALs are amazingly cheap. > Phil Ngai +1 408 749 5720 Actually, while PALs are great to work with and great to prototype with, their cost can be prohibitively high if you're going to mass produce something. For the cost of a PAL or a PAL-and-a-half (depending on the PAL), I can put a application specific gate array into my design which will easily replace the functionality of 4-10 PALs or more. On the other end, TTL still makes sense for very small operations (garage shops, hobbiests) who don't have their own PAL programming capability. Once you start talking 10ns parts instead of 25ns or 35ns, you've probably doubled you cost. No big deal if its a $20,000 system that you make 100 of a month, but a big concern if its a $100 system that you make 20,000 of a month. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dave Haynie {caip,ihnp4,allegra,seismo}!cbmvax!daveh "You can keep my things, they've come to take me home" -Peter Gabriel ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
miller@loral.UUCP (BIG DAVE) (01/20/87)
In article <571@vu-vlsi.UUCP> colin@vu-vlsi.UUCP (Colin Kelley) writes: >I'm looking for a 1-of-8 decoder (like the 74138) but with active high >outputs. I've looked through several TTL data books, but I haven't been >able to find one. This isn't exactly crucial, as the same effect can be >had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs >to my design after paring the chip count down so carefully with some neat >ICs (like the 74259). > Try a 74F538 (Signetics or Fairchild), Colin. It seems to fit your requirements, it's multiple sourced, and costs around $4.15/ea (100 piece price). Good luck, BIG DAVE. -- David P. Miller - Loral Instrumentation. / USUAL \ {sdcsvax,sdcc3} loral!miller \ DISCLAIMER / ******************************************************************************** "Ai, mas que saudades eu tenho da' Amelia, isso sim que era mulher ....."
reichel@cookie.dec.com (01/21/87)
---------------------Reply to mail dated 19-JAN-1987 02:26--------------------- >I'm looking for a 1-of-8 decoder (like the 74138) but with active high >outputs. I've looked through several TTL data books, but I haven't been >able to find one. >.... >Is an active high decoder really all that uncommon, or was I just unlucky >in my selection of data books to check? > >Thanks! > > -Colin Kelley ..{cbmvax,pyrnj,psuvax1,bpa}!vu-vlsi!colin After looking through several data books, the only 1-of-8 decoder I could find that may be of interest was a 74F538 in the Fairchild FAST logic series. This may be overkill as it has 3-State outputs, a polarity control to determine whether the outputs are active HIGH or active LOW, and three enable inputs for expansion to larger decoders. Also it is a 20-pin package. Hope this helps! John Reichel Digital Equipment Corp.
koko@uthub.toronto.edu (M. Kokodyniak) (01/21/87)
> In article <571@vu-vlsi.UUCP> colin@vu-vlsi.UUCP (Colin Kelley) writes: > >I'm looking for a 1-of-8 decoder (like the 74138) but with active high > >outputs. I've looked through several TTL data books, but I haven't been > >able to find one. This isn't exactly crucial, as the same effect can be > >had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs > >to my design after paring the chip count down so carefully with some neat > >ICs (like the 74259). > > Get with it, guy! Where have you been the last six or so years? Use a > PAL. TTL is obsolete and dead. For high speed, PALs come in D > varieties which run at about 10 nS, and that gives you a trip through > an AND-OR plane. For low cost, the plastic PALs are amazingly cheap. > New PALs provide buried state registers for implementing synchronous > state machines. Programmable polarity outputs mean an end to > DeMorganing equations. There are many new innovations such as UV > erasable, EE erasable, RAM programmed (great for debugging), *large* > arrays, programmable sequencers etc. All designers should have PALs > as part of their collection of tools. > > Note: PAL is a trademark of Monolithic Memories but we make them too. > -- > Social security is welfare for the elderly. > > Phil Ngai +1 408 749 5720 > UUCP: {ucbvax,decwrl,hplabs,allegra}!amdcad!phil > ARPA: amdcad!phil@decwrl.dec.com I agree with you that PAL's are great, but to replace three chips with a PAL is overkill (like trying to kill a bird with an anti-aircraft gun). TTL is far from dead! Even with PAL's, some TTL glue logic will probably be necessary. Besides, not everyone has access to programming tools needed for programming PAL's. Furthermore, haven't you heard of Fast (F-series) and Advanced (ALS-series) TTL? These afford greater speeds than standard TTL, if such is needed. I don't understand why engineers and technical people always have to be so gung-ho about technology and insist that nothing short of the leading edge of technology is good enough for them. I assume some humility and am quite content riding the falling edge of technology. Besides, I am not that lazy that I would always insist on the rising edge just to save time and effort. Furthermore, I appreciate that the falling edge can sometimes save me money. And now, I get back to the problem at hand without condescending flames. Look up the data sheets for 74ALS538. It is a descendant of 74LS138, but has "three-state outputs, output polarity control [as you want], multiple enables for expansion, data multiplexing capability", according to the Texas Instruments TTL Pocket Book (1984). It comes in a 20-pin DIP (as many PAL's do, but consumes less power). It offers a one-chip solution to your problem. However, this chip might be a bit pricey and may be difficult to obtain through an average consumer dealer. (This latter statement is just speculation on my part.) I hope that I have been of some help. Sincerely yours, Mike Kokodyniak
colin@vu-vlsi.UUCP (Colin Kelley) (01/22/87)
Thanks to everyone who was kind enough to help out. The suggestions I received
fell into four categories:
1. phil@amdcad.UUCP (Phil Ngai): USE A PAL!
I guess I should have mentioned in my posting that I'm a student, and I need
this IC for a senior project. I actually had to get the EE Dept. here to
order an EPROM burner! I guess they'll have a PAL programmer in about 25
years. Maybe AMD has a school-donation program?
2. phred!loreng (Loren Gahnberg): 74HCT238
I don't have any data books here that list this IC, but I see JDR (the mail-
order place where I usually get this stuff) carries them for $1.49. Not
bad at all...
3. reichel@cookie.dec.com, kvvax4!truls (Truls Ellefsen),
herzog@leadsv.LEADS.LMSC.COM (Jordan Herzog), kontron!andyt (Andy Thornton):
74F538 or 25LS2538
These sound like pretty snazzy chips, with enables and tri-states and an
output polarity selection pin. Dave Miller mentions a price of $4.15/ea, but
I see that JDR carries the 25LS2538 for $3.74/ea, as compared with $.39 for
the plain old 74138...
4. LOTS of people: 74259
This is a neat solution because I've already got a couple spare. It's a
little slower than the others, but that's not problem. BTW it goes for $1.29.
Thanks again for all your help. I apologize if I wasn't able to respond to
your suggestions individually...
-Colin Kelley ..{cbmvax,pyrnj,psuvax1,bpa}!vu-vlsi!colinjon@eps2.UUCP (Jon Hue) (01/22/87)
In article <14394@amdcad.UUCP>, phil@amdcad.UUCP (Phil Ngai) writes: > In article <571@vu-vlsi.UUCP> colin@vu-vlsi.UUCP (Colin Kelley) writes: > >I'm looking for a 1-of-8 decoder (like the 74138) but with active high > >outputs. I've looked through several TTL data books, but I haven't been > > Get with it, guy! Where have you been the last six or so years? Use a > PAL. TTL is obsolete and dead. For high speed, PALs come in D (vu-vlsi == Villanova University) C'mon Phil, lighten up. Remember what it was like being in college? I don't remember bins of EPALS, Stag PAL programmers, or CUPL running on Sun workstations. I do remember protoboards, 74LS parts, programming EPROMS on an HP64000 and a TA that couldn't speak English. The only people my age (23) I know that used PALs in college as undergraduates went to Stanford. Without walking over to my bookcase, I have found the TI 74HCT238 in the high-speed CMOS databook. Don't know if you can find it in LS or ALS, but the HCT will work with LS parts. The 238 is like the 138 except the outputs are inverted. By the way, how does everyone like the new logic symbols? I like them, you can tell what a chip is doing without looking at the logic diagrams. "If we did it like everyone else, Jonathan Hue what would distinguish us from Via Visuals Inc. every other company in Silicon Valley?" sun!sunncal\ >!leadsv!eps2!jon "A profit?" amdcad!cae780/
wsr@lmi-angel.UUCP (01/22/87)
In article <> colin@vu-vlsi.UUCP (Colin Kelley) writes: >I'm looking for a 1-of-8 decoder (like the 74138) but with active high >outputs. I've looked through several TTL data books, but I haven't been >able to find one. This isn't exactly crucial, as the same effect can be >had with a 74138 + 1 1/3 7404s, but I hate to go adding another two ICs >to my design after paring the chip count down so carefully with some neat >ICs (like the 74259). Why not use a PLA/PAL? You could probably squeeze your design *much* further with one of these. Check with AMD, Monolithic Memories Inc, Signetics, TI, etc for spec sheets. -wsr -- Wolfgang Rupprecht {harvard|decvax!cca|mit-eddie}!lmi-angel!wsr
berger@clio.UUCP (01/23/87)
Phil, I hope AMD supports PAL's better than MM. MM no longer gives out programming information for their new B series PALs. A commercial programmer is prohibitively expensive for most small users, especially compared to a couple of cheap LS chips.
henry@utzoo.UUCP (Henry Spencer) (01/25/87)
> Get with it, guy! Where have you been the last six or so years? Use a > PAL. TTL is obsolete and dead. For high speed, PALs come in D > varieties which run at about 10 nS, and that gives you a trip through > an AND-OR plane. For low cost, the plastic PALs are amazingly cheap. > New PALs provide buried state registers for implementing synchronous > state machines. Programmable polarity outputs mean an end to > DeMorganing equations. There are many new innovations such as UV > erasable, EE erasable, RAM programmed (great for debugging), *large* > arrays, programmable sequencers etc. All designers should have PALs > as part of their collection of tools. Love to. Will you write a cheque for the $25,000 or so I need to add all these goodies to my basement shop? PAL programmers are not at all cheap, especially ones that will program the latest-and-greatest. (You generally can't try to homebrew, even if you're competent, because most of the PAL suppliers don't tell you how to program them.) I won't even mention bozos like Altera that make wonderful-sounding chips -- big arrays of logic, CMOS so the power is manageable, fast, and UV erasable -- but package them as a "pig in a poke" deal with their own CAD software and their own programming hardware... -- Legalize Henry Spencer @ U of Toronto Zoology freedom! {allegra,ihnp4,decvax,pyramid}!utzoo!henry
larry@kitty.UUCP (01/26/87)
In article <7558@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes: > > [Discussion about PAL's...] > > ... I won't even mention bozos > like Altera that make wonderful-sounding chips -- big arrays of logic, CMOS > so the power is manageable, fast, and UV erasable -- but package them as a > "pig in a poke" deal with their own CAD software and their own programming > hardware... At least the Altera CAD software like Alterans (tm) and LogicMap (tm) runs on under MS-DOS on a simple PC. The Altera programmer also plugs into the PC, occupying one full slot. I have seen worse over the years - like design software which only runs on a VAX, or on a $ 25K development system. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|bbncca|decvax|nike|rocksanne|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {hplabs|ihnp4|mtune|seismo|utzoo}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
phil@amdcad.UUCP (01/27/87)
In article <359@uthub.toronto.edu> koko@uthub.toronto.edu (M. Kokodyniak) writes: >Besides, not everyone has access to programming >tools needed for programming PAL's. Sorry, I wasn't (perhaps I should have looked harder) cognizant of the original poster's University location. The proliferation of different parts and the difficulties in programming them is quite a problem with no easy solution I can see. >I don't understand why engineers and technical people always have to be >so gung-ho about technology and insist that nothing short of the >leading edge of technology is good enough for them. I assume some >humility and am quite content riding the falling edge of technology. The design/manufacturing/marketing cycle is lengthy enough that if you don't start slightly beyond the state of the art, you will be antiquated when your product finally reaches the market. Isn't it embarassing to offer a computer with say 64K bytes of RAM when everyone else has 256K bytes, in the same space and for the same price? Also, a reputation for offering the best/fastest products is very potent advertising. >Besides, I am not that lazy that I would always insist on the rising >edge just to save time and effort. Furthermore, I appreciate that >the falling edge can sometimes save me money. The main question is, are you making just one or are you designing a product? The design rules depend on this. I was speaking to people who make from 10 to 10,000 of something. Other volumes call for different methods. -- Paul Slansky: Those who believe that President Reagan had to have known about secret fund diversions to the Contras are overlooking Reagan's hard-won reputation for knowing practically nothing. Phil Ngai +1 408 749 5720 UUCP: {ucbvax,decwrl,hplabs,allegra}!amdcad!phil ARPA: amdcad!phil@decwrl.dec.com
apn@.UUCP (01/27/87)
in article <14491@amdcad.UUCP>, phil@amdcad.UUCP (Phil Ngai) says: > In article <359@uthub.toronto.edu> koko@uthub.toronto.edu (M. Kokodyniak) writes: >>Besides, not everyone has access to programming >>tools needed for programming PAL's. > >>I don't understand why engineers and technical people always have to be >>so gung-ho about technology and insist that nothing short of the >>leading edge of technology is good enough for them. I assume some >>humility and am quite content riding the falling edge of technology. > >>Besides, I am not that lazy that I would always insist on the rising >>edge just to save time and effort. Furthermore, I appreciate that >>the falling edge can sometimes save me money. > > The main question is, are you making just one or are you designing a > product? The design rules depend on this. I was speaking to people who > make from 10 to 10,000 of something. Other volumes call for different > methods. > > -- PAL's, IFL's, etc. PAL logic is great for some areas, and I have used it, however, please don't be so niave as to leave out one damn important factor: (see #3 below) if an off the shelf ttl or whatever (substitute your favorite logic family here) is available or maybe will come in 2 packages instead of one as compared to a PAL, then the "discrete" design is still quite likely the win. PAL's have several serious problems: 1] they are usually not as fast as the same implemtation in some other logic... say MSI/SSI ttl 2] they tend to consume more power than is needed for the same effective circuitry. 3] they almost always cost more!! For example: lets combine a few SSI/MSI ttl packages say a '08 and a '02 and an '04 total cost in TTL is about $0.50 in small quantity for a simple, non-registerd PAL we get $3.00, and price does not go down much, even in large quantity of say, 25k pieces. Is this worth the savings in board space ? Well... everything must be weighed. I just seem to find it hard to tolerate individuals that jump the gun and insist on using a PAL for the *most* trivial of logic designs. -- Alex P Novickis UUCP: {seismo, sun, ihnp4, 'etc' }!ptsfa!nonvon!apn {* Only those who attempt the absurd ... will achieve the impossible *} {* I think... I think it's in my basement... Let me go upstairs and check. *} {* -escher *}
phil@amdcad.UUCP (01/27/87)
In article <16200001@clio> berger@clio.Uiuc.ARPA writes: > >Phil, I hope AMD supports PAL's better than MM. MM no longer >gives out programming information for their new B series PALs. >A commercial programmer is prohibitively expensive for most >small users, especially compared to a couple of cheap LS chips. All the data sheets I looked at have programming information on them. Contact your salesman for a copy of the _Programmable Logic Handbook/Data Book_, 1986-1987. -- Paul Slansky: Those who believe that President Reagan had to have known about secret fund diversions to the Contras are overlooking Reagan's hard-won reputation for knowing practically nothing. Phil Ngai +1 408 749 5720 UUCP: {ucbvax,decwrl,hplabs,allegra}!amdcad!phil ARPA: amdcad!phil@decwrl.dec.com
hurf@batcomputer.UUCP (01/28/87)
AMD DOES have a university gift program or has had in the past.
They were kind enough to give Cornell EE a dollar amount to spend and some
data books about two years ago. The amount was generous without being
overkill - I doubt we've used it all. If Phil can't put you in touch
with their people who do this I may be able to dig a name up. The people
who took advantage of the program really appreciated it. - I believe it
was an unsolicited gift as well.
Hurf Sheldon Arpa.css: Hurf@ionvax.tn.cornell.edu
Lab of Plasma Studies
369 Upson Hall phone: 607 255 7267
Cornell University
Ithaca, N.Y. 14853