Hardware project - what logic-family to use?

[Kchula-Rrit]

It's a terrible title, but I could not think of a better one.

 

I'm getting ready to build some add-on hardware for my TI99, so I dialed-up the Digi-Key Web-site.  They have an alphabet soup of part numbers (they call it "series") for logic gates and such.  For example, I was looking for a 7432, which is a 2-input OR gate with four of them in a 14-pin DIP package.  If I recall correctly, the options I found were

7432

74LS32

74S32

74HCT32

74AS32

74ALS32

74ABT32

74F32

74ACT32

74ACTQ32

74AHCT32

74ABT32

 

The first three I've used when I built computers, back in the 1980s, and I'd heard of 74HCT parts but never used them.  The 'good old' 74LS32 is a lot pricier (~ $1.10) than all the others, except for the plain 7432 (~ 2.40!).  Tentatively, I'm going with the 74HCT family, as I remember it is supposedly TTL compatible.

 

Would that be the best choice, or should I bite the bullet and go for LS parts?  I'm thinking of logic levels, drive capability, speed, etc.  Advice from more knowledgeable (and less "rusty") folks is much appreciated.

 

K-R.

 

[+FarmerPotato]

39 minutes ago, Kchula-Rrit said:

It's a terrible title, but I could not think of a better one.

 

I'm getting ready to build some add-on hardware for my TI99, so I dialed-up the Digi-Key Web-site.  They have an alphabet soup of part numbers (they call it "series") for logic gates and such.  For example, I was looking for a 7432, which is a 2-input OR gate with four of them in a 14-pin DIP package.  If I recall correctly, the options I found were

7432

74LS32

74S32

74HCT32

74AS32

74ALS32

74ABT32

74F32

74ACT32

74ACTQ32

74AHCT32

74ABT32

 

The first three I've used when I built computers, back in the 1980s, and I'd heard of 74HCT parts but never used them.  The 'good old' 74LS32 is a lot pricier (~ $1.10) than all the others, except for the plain 7432 (~ 2.40!).  Tentatively, I'm going with the 74HCT family, as I remember it is supposedly TTL compatible.

 

Would that be the best choice, or should I bite the bullet and go for LS parts?  I'm thinking of logic levels, drive capability, speed, etc.  Advice from more knowledgeable (and less "rusty") folks is much appreciated.

 

K-R.

 

You missed some families ?

 

LS or HCT or a mixture will be fine. If you compare the speeds, you may find that some LS devices have an edge. but it’s unlikely to matter in the 4A. 
 

You should download all the data sheets for parts you want, and look up some things to compare. Like the A/C switching characteristics: time to propagate input to output. 

when you make that table for yourself you may find that some parts between two families don’t follow the general rule. Maybe because they are a revised, improved version.  

if speed matters, check for an ALS part. If speed really matters, consider a PLD like a 22V10 which will smush down the time to evaluate a complex expression. 
 

Also calculate how many loads an output can drive. You shouldn’t run into any problems but knowing is part of the design. 

 

Eventually you will want to use a 3.3V part. These can be interfaced using LVC245A which are 3.3V but accept 5V inputs. LVC parts output a high voltage which is still above the Voh minimum for LS.  The LVC125 is another to consider. 

TI.com has some guides like Designing With Logic.  try those. 

 

[Kchula-Rrit]

I'm sure I missed some, just used a 7432 as an example.  TI's "Logic Data Book" (just a PDF, really) lists single-gate chips with six pins!

 

Thanks for the advice; I'll check the guides.  Much appreciate the advice about the LVC parts, because one of my future projects involves a micro-controller that might not be available in a 5V version.  Looks like I have a bit of brushing-up to do before picking up the soldering iron.

 

Sometimes I feel like Rip van Winkle...

 

K-R.

[atrax27407]

You might want to try the Unicorn Electronics website as well (they are Hodge16 on eBay). I have never had a faulty chip from them.

[+FarmerPotato]

I guess you will try breadboard first?   Have you used wire-wrap?

 

My favorite sources for ICs and surplus
 

https://www.mouser.com/

 

Phoenix has a great website. In PEConnectors it is easy to find that component you don't know the name for.
https://www.peconnectors.com/index.php?p=home

 

Like atrax27407 said, our friend at Unicorn has always stocked good parts, which  we usually need for  kit builds.
https://www.unicornelectronics.com/

 

Great new stuff. Get their specials email:
https://www.goldmine-elec-products.com/

 

Hard to browse, big junk pile, but tons of TI logic chips.
https://www.electronicsurplus.com/

 

I'm a Mouser guy rather than Digi-Key, because I get amazing next-day delivery from Mouser Ft Worth.  Also SparkFun, AdaFruit, Jameco.

 

Source for 4A side port connectors
Ksarul or I can probably share if you just want one.

https://www.digikey.com/en/products/detail/hirose-electric-co-ltd/CR22A-44D-2-54DSA-70/5148616
https://www.digikey.com/en/products/detail/sullins-connector-solutions/ECC22DRMN/4547042

or just build onto a JediMatt42 TiPi style (I can't find 44 pin, but here's 40 pin long)
https://www.peconnectors.com/female-headers-pcb-2x-row-.100/hws16501/

 

[Kchula-Rrit]

Thanks for the links!  More cool stuff to check out.  Forgot about Mouser; they helped me with some "weird" connectors for our telescope when Digi-Key didn't have them.

 

I'm out in "the middle of nowhere", so overnight service is pretty pricey no matter what.  Martin Jones (www.mpja.com) charges a pretty penny to ship anything more than UPS ground, so I can't be in a hurry.  I don't know if it is because I'm 3000 miles away, or why.  Parts Express (www.parts-express.com) isn't a whole lot closer, but their shipping is much cheaper.

 

K-R.