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  • Author Author: baldengineer
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Are you still using 7400-Series Logic, if so, where?

baldengineer

Over the past several months, I have been learning about and repairing 8-bit computer and video game systems. So far, I have worked on the VIC-20, C64, ZX-81, Apple II, and have been learning about the TI 99/A.

 

It always amazes how much of these early computer systems were built almost entirely with standard 7400-series (LS and HC) chips.

 

Occasionally, I need to replace a 7400-series chip. (I always hope it is one of those and not one of the ASICs!) While looking for modern replacements, I have noticed the trend that they are becoming more scarce. The LS-series is almost entirely gone--and with good reason. While HC and HCT continue to be somewhat available, they are usually only available in surface-mount packages.

 

That leads me to the question: Who is still using the venerable 7400-series logic chips today?

 

To me, there are three groups that might be using them:

  1. Learning. Students and hobbyist learning about digital logic
  2. New Design. Hardware that needs glue-logic. Are these using multi-gate chips or the single-gate variants?
  3. Repair. Older electronics in need of replacements. Here is where I mostly sit.

 

Do you fit into one of those categories? If not, where do you land?

 

And THEN, which chips are the must-have on-hand?

Obviously, the answer depends on how you might be using them. But, I'm curious to know how you use 7400-series chips and which ones would you keep in stock?

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  • According to my lecturers, the 74-series is useful for small glue logic. But for large glue logic, a CPLD is much cheaper, and easy to modify design anytime even after building the circuit PCB.

     

    Recently in school (diploma level) it appears the curriculum is shifting to add some basic CPLD knowledge. I learnt the 74-series but also learnt some simulation by creating schematics in Intel Quartus software.

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  • According to my lecturers, the 74-series is useful for small glue logic. But for large glue logic, a CPLD is much cheaper, and easy to modify design anytime even after building the circuit PCB.

     

    Recently in school (diploma level) it appears the curriculum is shifting to add some basic CPLD knowledge. I learnt the 74-series but also learnt some simulation by creating schematics in Intel Quartus software.

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