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Questions tagged [ttl]

Transistor Transistor Logic. Logic circuits built from bipolar transistors and resistors.

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Designing a particular clock cycle series with glue logic/CMOS/TTL for serial data without a uP

I am looking to design an interface for serial data that runs for 31 cycles (not 32, I know), but with uneven cycles to transmit serial data. Each cycle is 8 clock pulses (at 7MHz). For the first 20 ...
paraparabolic's user avatar
0 votes
3 answers
40 views

Use digital sensor with USB to serial TTL converter?

I have a sensor (HC2A-S3A), which provides analog and digital output signals. The digital interface is UART (19200 baud, protocol RoASCII). Can I use a USB to Serial TTL Converter (chipset: FTDI ...
Pontis's user avatar
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Prolific PL2303 knock-off USB-TTL adapter without timing crystal

I recently got this bare-bones USB-TTL adapter which unsurprisingly contains a knock-off Prolific chip but on top of that it is entirely without the crystal oscillator. It seems to be missing some ...
Jamesfo's user avatar
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4 votes
2 answers
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What is this chip enable circuit doing? (old TTL, with diode, with pull-up?)

I'm trying to understand a small portion of a (vintage, TTL) circuit design and I'm a little unsure of what's going on in this section*, which determines whether the Chip Enable signal on a particular ...
BZo's user avatar
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1 vote
1 answer
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recognising patterns in TTL logic analog circuit

There is a circuit based on TTL( transistor transistor logic I think) . The signals at points A B C D are described. I am new with this TTL, could you help me decompose this united circuit into the ...
Chris95's user avatar
3 votes
1 answer
349 views

Using a function generator as a clock source to drive several ICs (CD4000 CMOS series & 74 TTL)

I am building a circuit that uses a 4 MHz reference carrier. The used ICs are basically XOR 7486 and NOT 7404, CD4013 flip-flop, etc. I have a function generator which is capable of providing up to 5 ...
Mohamed Abuain's user avatar
2 votes
2 answers
128 views

What is a simple circuit to generate TTL signal with fixed frequencies?

What is the simplest circuit that can be used to generate a 5V TTL signal with fixed frequencies such as 0.5Hz, 1Hz, 50Hz, 100Hz, 500Hz, 1kHz, 5kHz, 10kHz..?
Shamooooot's user avatar
0 votes
4 answers
308 views

Level shifting from 3.3V to 5V not working: voltage drops when attaching load

I am trying to trigger a laser using an Arduino. I used a power supply to determine that the laser needs a 3.5V (or higher) signal, at which point it draws around 2.2mA from the power supply. When ...
Timeverdrive's user avatar
1 vote
3 answers
111 views

Simple TTL: Is there a way to "detect" a high-z state and easily use that to drive other logic?

I have two TTL style logic chips, call them A and B (*), where the outputs of A are the inputs to B (think: 8 data lines). A has tri-state outputs, so when they are turned off they float. B is an ...
BZo's user avatar
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2 answers
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Turn TTL high output signal into ground pulse for EEPROM write

I have a TTL-high output signal which I wish to use to send a negative pulse to a 28c256 EEPROM WE pin to write to it, but the high line may remain high until the next clock signal/output change etc. ...
Hektor's user avatar
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12 votes
4 answers
2k views

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 ...
BZo's user avatar
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1 vote
2 answers
372 views

Is it okay to call a UART “RS-232” if it doesn’t respect voltage levels specified in the RS-232 standard?

I have been using this converter call it converter A to communicate an MCU through its UART pins RX TX. And I wouldn't call this RS232 because RS232 is about physical layer and voltage levels as ...
pnatk's user avatar
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1 vote
0 answers
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Latch circuit to cycle power in an ATX PSU

I'm designing a system powered by an ATX PSU. I'd like it to be able to be switched on and off by a momentary switch but also to be able to be turned off by another input. The latch circuit is powered ...
DusteD's user avatar
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2 answers
295 views

May I connect the RO and DI pins of a MAX485 module directly to ESP32 pins?

I'm running my MAX485 module board with an external 5V power supply, with the R0 and DI pins from the module connected directly to the ESP32 pins, which running at 3.3V. Both grounds were not tied ...
Kenny Thum's user avatar
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0 answers
26 views

Why would I use HNM (high noise margin) gate drive over a TTL gate drive for DC motor driving application?

I am making a very simple half bridge DC motor drive using the MAX1760 gate driver. Looking through the datasheet I saw that it offers two types of logic level technologies (if that's the right word?);...
tronhawk's user avatar
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1 vote
0 answers
199 views

How to obtain the counting of TTL pulses from an FPGA?

I'm currently working on a project in which I need to program an FPGA in order to connect it to a photon detector, that generates a TTL pulse when detecting a photon; I need to count this pulses, ...
Jorsa's user avatar
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0 votes
2 answers
69 views

Tie an enable pin to ground when another pin is high

I am designing a simple circuit with two ICs. IC1 has an enable pin that is internally pulled up with a 10Kohm resistor. To disable IC1 you have to tie this pin to ground. IC2 has an serial presence ...
mwp's user avatar
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1 vote
3 answers
146 views

Converting a 74LS74 and a 74LS193 to CMOS. What inputs need pullups and what needs pulldowns

I have a circuit I traced out off an old, dead PCB that came from the early 90s. It was using TTL chips back then. One thing I noticed is that it has a dual flip-flop. One flip-flop is being used as a ...
Erik Vincent's user avatar
0 votes
2 answers
98 views

Need help identifying circuit diagram symbol

In the datasheet for Hamamatsu s13131-1536 CMOS line sensor(https://www.hamamatsu.com/content/dam/hamamatsu-photonics/sites/documents/99_SALES_LIBRARY/ssd/s13131-1536_kmpd1159e.pdf) there is this ...
Mikhail Seryukov's user avatar
1 vote
3 answers
98 views

Generating TTL-level signal from an analog fast pulsed high-voltage DC signal

I am exploring feasible ways to design a circuit to generate TTL-level digital signal from an analog pulsed DC voltage output. The voltage range of the pulsed DC signal can be from 0 V to 3 kilovolts ...
Allison's user avatar
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1 vote
2 answers
131 views

Converting a fast-switching 0-2.5V input to TTL signal

Dear fellow engineers, I am attemping to convert a fast switching (~ns) 0V - 2.5V pulse from FPGA into a TTL-standard (0V - 5V) signal. I have been browsing for voltage regulators online. Most of them ...
Boan Fang's user avatar
0 votes
2 answers
79 views

Is it possible to connect ATMEGA328 to type-C and read data without a USB-TTL converter?

there was a task to create the most compact device with atmega328 on board, but the question arose whether it could read data from type-c without a ttl converter ...
Settings's user avatar
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2 votes
1 answer
188 views

Turn on/off a LED using a D-FF and a transistor

I'm trying to control a LED using some microcontroller and I designed a circuit using a D-FF and a transistor to handle it. It looks like this: So I can control when to turn it on or of by simply ...
sergiopolog's user avatar
6 votes
1 answer
257 views

Active pull-down in LSTTL totem-pole output

The lower totem-pole transistor of a LSTTL IC frequently has an active pull-down from base to emitter (ground). Here is an example from TI's SN74LS93 datasheet. I was curious how this active pull ...
Math Keeps Me Busy's user avatar
0 votes
2 answers
128 views

What is the application of the 74LS373?

Looking at the truth table, the data from the D(n) input are directly transferred to the Q(n) output when the high state appears at the C (CLK) input. If there is a low state, there are no data at the ...
Jerzy Przezdziecki's user avatar
2 votes
2 answers
402 views

3V oscillator to 5V µC with an 74HCT inverter (12.8 MHz) - bad idea?

I'd like to use an AVR (ATmega328P-AU to be precise) in combination with a fairly accurate oscillator for timing purposes. I stumbled upon the fact that oscillators which have greater accuracy mostly ...
Korbinian's user avatar
2 votes
4 answers
463 views

Convert a 0 V / 3.3 V trigger signal into a 0 V / 5V trigger signal (TTL)

I have a device sending a square trigger signal 0V / 3.3V, with a BNC connector. (We usually call it a TTL signal, I don't know if it's the common name? is it relative to Transistor-Transitor-Logic?) ...
Basj's user avatar
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1 answer
302 views

MAX3232 ESE+ Not Working but ST3232C and MAX3232 Working on same PCB

I have designed a pcb for Rs232 to TTL, UART converter for using ESP32. I will control an LCD with ESP32. Some IC's (MAX3232 ESE+) heating at the first start. and not working just heating and heating. ...
mehmet's user avatar
  • 1,139
0 votes
6 answers
1k views

Output voltage level of TTL gate

The output voltage level of the TTL logic family is from 0 to 0.4 volts (LOW) or 2.4 to 5 volts (HIGH). Suppose we have a TTL inverter with a square wave of 5 volt amplitude as input (0 volt and 5 ...
MAJID AHMAD's user avatar
0 votes
1 answer
148 views

TTL bus termination physical circuit layout

I'm breadboarding a simple data bus terminator for a 1970s TTL computer bus that was normally unterminated. I'm trying both passive and active termination to see how they work, but have a question on ...
BZo's user avatar
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0 votes
2 answers
193 views

How to use SMA port for RF Switch's TTL Control?

I am considering purchasing this RF switch from Eravant (previously sage), and I realized many of its SPDT RF switches are using a SMA female port as the control logic input to the TTL driver, whether ...
Power_tile's user avatar
0 votes
1 answer
288 views

Understanding passive TTL termination

I've been working with 1970s devices and an unterminated system bus. I am adding termination to that but want to first understand a circuit that I have seen to make sure I understand what's going on. ...
BZo's user avatar
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1 vote
1 answer
106 views

How to double a single TTL to link to 2 independent TTL terminal

I am working on a project that needs multiple serial connection between mcu sensors . In order to send data by ttl serial from 1 mcu to 2 other mcu and reverse... What is the best way to achieve this ...
Khales Naim's user avatar
2 votes
2 answers
344 views

Load bootloader on ESP32

I'm trying to load the bootloader to my esp32 or that's what I think I need, because when I connect it with USB to TTL, and I connect TX with RX, Rx with TX and GND with GND and I reset the micro by ...
Maxpower5859's user avatar
1 vote
2 answers
998 views

Driving a 12-to-24 V P-channel MOSFET with TTL

I'd like to control up to 16 motorized valves with an ESP32. I'm using 74HCT595 shift registers (5 V outputs, 3.3 V input logic) to drive 12 V relays via NPN transistors. But the relays are pretty ...
Ethan Arnold's user avatar
0 votes
2 answers
386 views

Create TTL pulse with button press

Is there any way to get a 5V TTL signal (pulse of whatever duration, could even be a boxcar) from a button press with a very simple circuit or with some consumer device? I need this to do some ...
TheChymera's user avatar
0 votes
0 answers
57 views

What is the quiescent power dissipated by a TTL totem-pole output stage?

In High-Speed Digital Design by Johnson and Graham, the quiescent power of a TTL totem-pole is given as: $$P_{quies} = \frac{0.4I_{sink} + 1.0I_{source}}{2}$$ I am fairly certain the 1.0 is a mistake ...
John Arg's user avatar
  • 209
17 votes
11 answers
2k views

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. ...
BZo's user avatar
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1 vote
1 answer
41 views

Interface higher voltage signal to 5 V pull down input signal circuit using discrete hobby components

I have a microcontroller, TTL logic that expects its input to be connected to the ground via a brake lever to tell the microcontroller that the brake has been applied. I believe it uses an internal ...
Scott's user avatar
  • 286
-3 votes
1 answer
129 views

Definitions of Serial TTL UART MCU acronyms

I was looking for a comprehensive list of terms and acronyms concerning serial peripheral communication including their descriptions and, crucially, how they relate to each other. Since this site ...
Jamesfo's user avatar
  • 256
5 votes
2 answers
605 views

TTL NAND gate analysis

I was looking into Millman's Microelectronics book, 2nd edition, pp. 245 - TTL NAND Gate. I am a beginner in electronics and was looking into this book just because of an assignment problem about a ...
curious_mind's user avatar
2 votes
2 answers
145 views

Debugging a problematic old TTL pull-up that's not pulling up

I am trying to bring back into operation a late-70s disk controller board (all 74xx TTL). I'm stuck trying to figure out why a small pull-up network is resulting in a far out of spec voltage not doing ...
BZo's user avatar
  • 2,121
0 votes
1 answer
66 views

Is AM29F040B CMOS EEPROM TTL Compatible

I can't really make any sense of the datasheet regarding whether the AM29F040B EEPROM can be used with TTL inputs, so wanted to ask on here. It is a 5V CMOS IC, but there are mentions in the datasheet ...
David777's user avatar
  • 1,511
2 votes
2 answers
234 views

Differential capacitance change measurement (sensing) with 74LS628

I'm researching the possibilities to accurately register the capacitance changes of a big metal plate (area 10 m2) to the ground (GND, yes - earth, soil). It varies around 100-200 pF. For now I'm ...
valioiv's user avatar
  • 73
0 votes
1 answer
25 views

Serial conection HMT310

How to connect the HMT310 via serial port? When I connect it and open PuTTY and put "?" for it to show me the data, it pulls all "U"s. I already checked that the baudrate and other ...
Maxpower5859's user avatar
2 votes
2 answers
2k views

TTL to RS485 using MAX485 - Capacitor voltage requests

I need to implement a TTL to RS485 converter into an home made project and searching by Google I found this module with related schematics: Could you help me by indicating the correct voltage for the ...
Simone's user avatar
  • 87
3 votes
1 answer
875 views

Why does the 74LS08 see an input logic level even if the inputs are not connected?

I have an 74LS08 (AND gate.) I did not connect any inputs to the IC, but it gives me voltage at the outputs. Should I separate VSS?
Mohammed Al-Elaiwi's user avatar
2 votes
4 answers
336 views

What is the correct maximum value for resistor R₁?

How do I calculate the maximum value of resistor R1 if the following values are known: VDD = 5 V inverter CMOS CD4069UB IIL = IIH = 0 mA VOH = 4.95 V VOL = 0.5 V IOH = IOL = 0.6 mA VD = 1 V maximum ...
Aleksa Majkic's user avatar
0 votes
1 answer
315 views

Communicating with 6 TTL devices that support the Modbus protocol

I am working on project using Hukseflux SR05-D2A2 thermal sensors. These sensors support Modbus communication through a TTL interface. The objective is to read the value at a specific address in the ...
RandomEye's user avatar
0 votes
2 answers
540 views

How do I know if it's RS232 levels or TTL levels

I have a random device: GT MEDIA V8 Finder Pro. I would like to communicate over its console port. Here are some pictures of its mainboard. Here is the area around the console connector: I have no ...
LimetaPeta's user avatar

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