Questions tagged [ttl]
Transistor Transistor Logic. Logic circuits built from bipolar transistors and resistors.
563
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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 ...
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8
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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 ...
- 1,609
22
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3
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What does a two overlapping circles symbol mean in an electrical schematic/diagram?
In the datasheet for a A3503 Hall Effect Sensor, I saw a circuit diagram labeled 'Functional Block Diagram', and it shows a symbol I have not seen before. It's shown here between 3 - Output and 2 - ...
- 1,181
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Why was so much TTL logic design "negative true"?
I've been spending time with schematics debugging busted 1970s TTL-based computing circuits. I'm sure this is a more general question but I'll ask it in this context since that's what I'm exposed to.
...
- 2,151
17
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2
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How does TTL serial work?
I've been trying to find a good description of the TTL serial "standard" without much luck. I understand that serial transmit (TX) and receive (RX) lines idle high (at VCC) and that they drop to ...
- 2,564
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4
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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 ...
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13
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How is this circuit for level converting (5V<>3.3V) working?
Does anybody know, how is this circuit exactly working? It is level converter between 5V and 3.3V logic and it is bi-directional.
I have some theory, but I am not sure with it (I never worked with ...
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12
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4
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When is it appropriate to mix 74LSxx components with original TTL 74xx?
I spend almost all my tinkering time with 1970s era logic circuits, which use almost all original 7400-series TTL. I do a fair bit of repair and am now starting to design additional logic to work with ...
- 2,151
11
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4
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Should I use CMOS vs. TTL?
Now, I know that this question has been asked so many times that it seems like I'm trolling, but I must point out that I couldn't find the right answer to this question anywhere.
So yeah, CMOS and ...
- 1,947
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Does this circuit have marginal voltage level problem?
As a research for the problem I described here I found this circuit by Maxim:
This is clock doubler, and must be a really good fit in my case as input frequency is very well defined.
However looking ...
- 7,120
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Buffering a Digital Microcontroller Signal for Connecting to an Optocoupler
I frequently work on projects in which I use optocouplers for isolating digital +5VDC control signals (for example, from a microcontroller) from the rest of the circuit. However, since these work by ...
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1
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How to convert a digital signal from 24V to 5V
I have an industrial automaton that gives me a digital signal (24V or 0V) on its outputs and I want this signal to control an integrated circuit, but the integrated circuit only takes a TTL signal in ...
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How to manufacture chip on board?
I am a developer of a cheap product and i have no experience in mass production. Device is fully functional and represents a single sided PCB, a microcontroller, a bunch of diodes and a few passive ...
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Rising edge pulse detector from logic gates
The circuits I describe are entirely made of 7400 series logic gates (7402, 7404 and 7408 ic).
I'm trying to build a rising (positive) edge pulse detector using logic gates.
The following circuit ...
- 309
9
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6
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Multiplexing UART
I'd like to interface my main microcontroller's hardware serial port to more than one device at the same time. My understanding is that UART on my microcontrollers is based on an active-low 5V TTL.
(...
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9
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Using HC/HCT, AHC/AHCT series logic
I am builing a circuit, and i need to connect a few different IC's (obiosly). My circuit is based on 5V TTL logic and i found a part that is made only in AHC/AHCT variant.
So let's take it from the ...
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Is it possible to program an STM32 with an Arduino?
I have one of these:
http://www.ebay.com/itm/111297094334?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
I know an USB-TLL dongle is usually used to program it, but I don't have one and I ...
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Do stateful 74LS series chips start in a defined state?
Specifically, 74161 counters and 74377 registers, can I rely on them to be full of zeros on power on?
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4
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10k Resistor Pull Up/Down Standard for 74 series chips
I've been having some issues lately with the usage of 10k ohm resistors as pull down resistors for 74ls series chips. Most people seem to choose 10k resistors as their default pull up/down value but I'...
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Connecting unused logic gates
Logic gates like AND, OR, NOT etc. often come packed as arrays in ICs.
Sometimes not all gates are used in a project. I would like to know how the remaining unused gates should be connected to ...
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In a 74HC14 Schmitt trigger IC, unused inputs/outpus
I have a 74HC14 Schmitt trigger IC. I only use one of its I/O pairs, and everything else is not used.
I understand that in TTL logic the unused inputs should be set to either high or low to prevent ...
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Bidirectional level swiching 5V <-> 3.3V
I am looking to interface a 3.3V device with a 5V one. This will require the shifting of the logic levels between the two devices.
Doing this in one direction is a trivial matter, but I need to do ...
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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 ...
- 1,753
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Capacitors in MAX 232
Out of curiosity, can I replace the electrolytic capacitors in the circuit with non-polar ceramic capacitors? Will I get the shifting in level?
MAX232 datasheet: LINK
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What is Namur, and how does it work?
I found a TTL converter box custom made many years ago. It says Namur_to_TTL converter on it. What is Namur? I googled but couldn't find a clear explanation.
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Tying open-collector outputs to TTL inputs
I know that open collector outputs are effectively either 0 V or high-Z.
I also know that TTL chips tend to read a disconnected output as high, but that really you should have something like a 1 kΩ ...
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1
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What to do with unused TTL and CMOS outputs?
Just about everything I've read on the Web, including on this site, say that unused TTL and CMOS outputs should be left floating. However, this TI article, Designing with Logic, states:
Unused ...
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1
answer
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TTL voltage shift from 5 to 3.3 Volts "UART"
I want to make serial communication with a device which works on 0-5 Volt TTL level. But my serial chip uses 3.3 Volt logic. (this is an UART communication)
I know that I need a step down at least ...
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2
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Current limiting resistors
I notice that in Ben Eater's project for the 74 series logic chip computer, which my son and I are building, sometimes he uses current limiting resistors on LEDs on the pins of some chips, and on ...
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2
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Interfacing Arduino to C64's tape port
Update: a practical implementation of this is done in the Tapuino project made by Peter Edwards. Check it out, everything is open sourced: https://github.com/sweetlilmre/tapuino
I'm working on a ...
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