Tagged Questions

5
votes
2answers
81 views

What should be considered when sizing trace widths for digital logic signals?

For traces that carry a static DC current, it's pretty easy to calculate the minimum trace width based on the required ampacity of the trace. However, I'm not sure what should be considered when ...
3
votes
2answers
89 views

Digital Clock --->Bad Accuracy (Help to Troubleshooting)

INTRODUCTION: I'm a student in the Electronic Engineering program at my University. I'm building a digital clock as a self initiative to learn more. Some of the requirements and steps that is ...
0
votes
2answers
116 views

Gating TTL UART Tx pin to simulate BREAK for arbitrary time periods

I need to gate a TTL Tx pin @115000bps as the chipset that drives the RxTx lines do not implement UART BREAK for arbitrary time periods. Thanks to this community's feedback (Selecting proper vales of ...
2
votes
3answers
278 views

Which 74xx logic families are overvoltage tolerant on their outputs?

Here's my dilemma: I have a 3.3v active-low logic line, and I want to use it to drive a 5v active-low logic line. The 5v line already has a pullup, so my plan was to use an open-collector buffer IC ...
2
votes
1answer
578 views

What is the fastest 7400 series family? Is 74VHC faster than 74AHC?

What is the fastest 7400 series logic family? Is 74VHC* faster than 74AHC*? This list does not seem to be in any particular order: http://en.wikipedia.org/wiki/7400_series
3
votes
2answers
190 views

Why is my XNOR output always low?

I recently bought some Texas Instruments TTL chips. So far they've been OK, except the XNOR (SN74HC266N) chips (I've tried 3, including one that's never been in my "real" circuit) always output low ...
13
votes
8answers
1k views

Is it worth it learning how to use 7400 series “jelly bean” logic IC's or are they completely obsolete?

My road map for learning electronics included the 7400 series logic chips. I started in on electronics by following the labs in the "Art of Electronics" lab manual which includes labs with these ...
11
votes
6answers
649 views

What are the advantages of using FPGAs over TTL in intro computer architecture?

I teach the one and only computer architecture course at a liberal arts college. The course is required for the computer science major and minor. We do not have computer engineering, electrical ...
1
vote
1answer
803 views

Creating a one-digit scoreboard using logic circuits

I'm creating a one-digit scoreboard on a breadboard. Naturally, I have a BCD to 7-segment decoder and a 7-segment display. But I don't know how to automatically increment the display. (It's for a ...
2
votes
3answers
554 views

Going from Transistors to Gates to…IC's?

So I am trying to understand I guess what is probably a basic concept of computers. I was taking a look at this previous question: From Transistor to Gates And it's accompanying link: ...
8
votes
2answers
286 views

What logic family is best for general-purpose hobbyist stuff?

I need to buy a few logic ICs. Which family should I get? HC? HCT? Which kind is best to have lying around in a parts box, for maximum compatibility with unpredictable future projects? Wide supply ...
2
votes
2answers
543 views

CMOS (or CMOS compatible) shift register with latched open-drain outputs

I've been looking for a 3.3V compatible shift register (SIPO) with latched open-drain outputs. I've settled on a 74xx596 (not a '595!), but of all the 74xx CMOS series I've been looking at omit this ...