Questions tagged [ttl]

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

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60 views

How to connect STM32F103C8t6 to computer when using USART?

I'm an electrical engineering student and I've just started to learn microcontrollers.I want to know is there any way to connect my board(I uploaded its picture)to computer when I'm using USART ...
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2answers
65 views

What DC Power Supply Do I Need To Get For This Device?

I recently bought a small 3 to 1 HDMI Amplifier Switcher. It can work without power adapter only if the 3 HDMI inputs are connected and supplying current. I want to operate it with only 2 input which ...
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1answer
63 views

Why cannot I use the USB port directly to communicate via PC with STM32F4-DISC

I will keep it short and clean, if it won't be enough please let me know and add more details. When using an Arduino UNO, a serial communication can be achieved by the same USB connection which is ...
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1answer
92 views

If you wire together two TTL outputs, which one wins?

If you connect together two outputs from 7400 NAND gates, which output will dominate - high or low? Background: I'm reverse-engineering a 1969 circuit board, and in multiple cases they tie together ...
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1answer
50 views

Will SN74HC245N transceiver support TTL RX when blocked?

I'm actually designing a system with: ~10 "Master" boards that transmit data from slaves boards to a RS485 network 4 "Slave" boards per master one, connected trough a 3 pin jack (5V, GND and half-...
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2answers
101 views

What's the difference between 74LS00 “gates” and 74LS37 “buffers”?

The TI 74LS00 is "quadruple 2-input positive-NAND gates" and the 74LS37 is "quadruple 2-input positive-NAND buffers." The pinouts are identical. The LCCC package is documented exactly the same for ...
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1answer
47 views

What's the phase relation between the sine wave and the sync output from a function generator?

I'm using a function generator to generate a sine wave, and am trying to use the sync (TTL) output to flash an LED at the beginning of each wave pulse. However, when I compare the sin wave and the ...
2
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1answer
81 views

Fundamental TTL circuit and its operation

So i am studying TTL circuits and i started with fundamental configuration as shown in the following picture. NOTE: Transistor Q1 is actually a two emitter transistor, i just couldn't find proper ...
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1answer
56 views

3.3V TTL is dropping to 2v when connected to pin [closed]

3.3V TTL is dropping to 2v when connected to pin. can i use a current limiting resistor in series to maintain 3.3v. Need suggestions.
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2answers
779 views

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 ...
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1answer
57 views

FT232R TTL Logic Levels

I have an FT232R chip hooked up to my oscilloscope with the TX and RX pins joined. I'm sending characters directly to it via Putty. The logic levels I am seeing are 5V low and 0V high. I thought the ...
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3answers
173 views

MAX232 Replacement

I have a circuit where a 12V square wave signal (a Profile Ignition Pickup signal from a Ford EDIS ignition module) was fed to an MCU via a MAX232 chip. My understanding of the MAX232 is that the ...
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1answer
74 views

Switch between USB and Bluetooth module TTL

In my project I have an MCU that I want to communicate with via 5V TTL serial. I have two methods of doing this in my circuit, USB via an FT232R (5V) and Bluetooth via an HC-05 module and level ...
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1answer
30 views

Pull down for 74HCTXX series logic ICs

I am building an adder with standard 74HC/HCT series logic ICs. I see the result when input pins are left floating are erroneous. Shall I have to connect some pull down resistors. Thank you.
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2answers
61 views

What specs does the “gros condo” (big capacitor) needs to have?

I have a pair of Dynaudio Air 20 at home. Unfortunately, the cable that used to control the speakers via RS232 died. I opened the cable, and saw that it was a customized RS-232 to TTL adapter, but ...
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0answers
44 views

Setting measurement points of the 74HC86 delay time

simulate this circuit – Schematic created using CircuitLab I'm measuring a propagation delay and transition delay of a 74HC86 chip. I setted somewhat high frequency square-wave signal(100kHz) ...
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2answers
81 views

Component recognition from marking code

I need help to recognize a dead component from a lab instrument control board. It is part of a TTL-serial interface, arguably a logic gate or some level shifter, in a TSSOP-14 package. You can see ...
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1answer
41 views

Unpowered 74ls chips vs Powered Nano?

I have a power-hungry 74ls digital logic project that I want to connect a USB-connected Arduino Nano to, but I'm not sure how design the interface between them safely. The project has an external 5V ...
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2answers
108 views

Converting a variable frequency to TTL HIGH and LOW levels, based on a fixed (possible non-fixed?) frequency

I have a square output from an LM324 op-amp (0 and 5 volts) which has a frequency between 1 to 500 Hz (yes, low frequencies). I would like to find a simple way to have HIGH TTL signal when it is over ...
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1answer
77 views

Supplying TTL Signal via USB

I have two pieces of hardware I'd like to interface with via USB. The first are 2002 Series Actuated Valves and the second is a Mass-Flo Controller for regulating gas exchange. To my (admittedly ...
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4answers
114 views

TTL Logic for displaying large 7-segment values [closed]

For fun, I was trying to imagine how I might implement large values in 74 series logic (or any commonly available discrete logic from the 1970s). An example might be displaying prime numbers up to ...
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3answers
71 views

TTL square wave inverter adjustable duty cycle

I am an amateur and I don't have experience with logic circuits so please forgive me if this is very simple. I have a 5V TTL crystal oscillator (4-pin). I need to create a second square wave from it ...
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1answer
103 views

STM32F407 CMOS or TTL or HC

I wonder which logic technology is STM32F407 MCU based on.. CMOS or TTL or HC or LVT etc? Although its mentioned in the datasheet that the GPIO's are CMOS and TTL compliant. I am concerned about this ...
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3answers
189 views

Interfacing GPIO 3.3V to 74HC04 5V

Will it be safe if I connect STM32F407 GPIO outputs (Vdd=3.3V) to 74HC04 hex Inverter inputs (Vdd=5V)? What is the best recommended method to add an inverter at the output of STM32F407 MCU? edit: ...
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1answer
81 views

PL-2303TA TTL UART data corruption

For a lot of projects, I use a fairly common USB to serial dongle called "Prolific USB to Serial" which uses a PL-2303 TA chip to allow USB to 3V TTL serial (i.e. this kind on Alibaba). I actually ...
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5answers
107 views

Will this 555 circuit prevent a car from disconnecting power to the radio when starting?

To start with I'm a little rusty with electronics, I haven't done much in 20 years and it was only a hobby back then. In my car I have a head unit with a touch screen which relies on software to run ...
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2answers
104 views

Can a TTL LS device (low-power Schottky) serve as an input to a basic TTL device?

A 74121 (One-shot) worked well as a reset to a counter device. There is an enable line using a 7400 NAND gate to allow or disallow the trigger to pass. While duplicating the circuit, I found that all ...
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2answers
179 views

What is the point of 2 inverters in series? [duplicate]

In the datasheet for the Nexperia HEF4543B, in the logic diagram, there are 2 inverters in series: What is the point of these inverters in series?
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1answer
234 views

Can't type on Virtual Terminal Proteus

I've connected my SIM900a module with PC via a USB to TTL converter. I'm using Proteus Virtual Terminal for check the AT commands. The problem is I can't type anything on the Virtual Terminal. Copy ...
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0answers
76 views

Why can't I get the output of a 74LS221 to idle at 5 VDC?

I have an industrial machine with an encoder feeding a Measurement Computing USB-CTR08 counter board. In order for the board to count the pulses the counter's gate ...
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3answers
98 views

TTL IC logic high output doesn't reach high enough voltage

I've been having a problem trying to build a breadboard circuit. The problem being, that some IC high outputs doesn't reach a high enough voltage, staying around ~2V. That is not sufficient for a ...
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1answer
35 views

Initial noise prior to square pulse

I have a high voltage system (~5kV) to generate pulsed spark. I was able to detect the spark ignition. It has been shown in the images by the yellow line. This signal will be used to generate another ...
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2answers
90 views

Are there still programmable clock synthesizers with single ended TTL output leves (in 2019)?

I'm looking for a clock synthesizer IC that can drive my vintage 5V NMOS CPU in the range of 5 - 50MHz. The granularity would preferably be in the range of 100kHz or less. All I can find when ...
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1answer
37 views

Optical receiver output voltage higher than power supply

The part is a optical receiver from Broadcom. It has TTL output, but specified with a maximum output-high voltage higher than the power supply. I wonder what's special structure internal may make it ...
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1answer
87 views

Questions about RS422 driver

I am using a GPS receiver board which transmits a PPS signal into a TTL <-> RS422 board I need to design. The receiving end (of the RS422 signal) is 15-20 meters away. Here is my design: My ...
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0answers
54 views

Serial communication between raspberry and laptop not giving right values

I want to communicate between a Raspberry Pi 3 model B and a laptop using a USB to RS-232 cable and this RS-232 to 3.3V TTL converter via the serial module in Python: GND is connected to board pin #6 ...
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1answer
121 views

Change serial converter voltage from 5 V to 3.3 V using resistor

I have a USD-TTL converter which uses 5 V. Can I change the output voltage from 5 V to 3.3 V using a resistor? Product: https://www.amazon.com/Breakout-USB-TTL-Module-Lilypad-ATmega328/dp/B01LQYO1AI/...
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0answers
32 views

UART Current in PIC18F46K22 & 7404 Input Current

I am currently making a decision to invert the UART signal from my PIC18F46K22 and have 2 choices to either use 74LS04 and 74HC04 but there is a difference between the LS and HC that the LS can output ...
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5answers
158 views

RS485 IC Termination Resistor Configuration

I've made a mistake on a design, that went into production... It was built like the drawing on the left, with R702 to 5V and R703 to GND, it should have been backwards... like the drawing on the ...
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2answers
127 views

Power issues on TTL circuit

I am building a homebrew 8-bit computer on breadoards and PCBs with TTL logic IC's (LS, HCT and ALS families). This is a small portion of the circuit (3 modules): I'm using an ordinary phone charger ...
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1answer
70 views

TTL gate characteristics

In case of BJT for example, the input characteristics can be described with \$I_B=f(V_{BE})\$ and output characteristics with \$I_C=f(V_{CE})\$. How can the input and output characteristics be ...
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2answers
98 views

74AS TTL to CMOS pull up resistor and maximum speed (or lowest delay)

Hello I have to pilot a CMOS input 5V chip device with a 7474 flip flop with the lowest possible delay to minimize clock jitter. Signal is about 11.3 Mhz I have two options: 1) 74HC74 (CMOS ...
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1answer
236 views

Clock signal generator using 7400

I have an old PCB that uses this clock generator (means I'm absolutely sticking to the schema). The IC is standard 7400, resistors are the same, but the capacitors I'm using have 470 uF (500's are ...
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1answer
109 views

What is the purpose of the Load transistor in a TTL Logic NOT gate?

My professor presented the NOT gate in the Transistor-Transistor logic as the following: Where V is always 5Volts. The two symbols are MOSFETs N-type transistors. The first transistor (which is ...
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1answer
848 views

Why do some Arduino-compatible boards provide a crystal for the CH340? [closed]

I have an uno-shaped Arduino compatible which uses the CH340(G) serial to ttl converter chip and it is connected to an external crystal. I also have nano shaped compatible which uses the CH340(C) ...
2
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1answer
304 views

What was the use-case for the 74hc590?

The 74hc590 http://www.ti.com/lit/ds/symlink/sn74hc590a.pdf is a binary counter followed by a register with a tri-state output. I thought about using it an a (homebrew cpu) design, as it's wider than ...
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1answer
128 views

Replacing CMOS SRAM with equivalent TTL SRAM

I want to replace an IS62WV51216BLL-55 (http://www.issi.com/WW/pdf/62WV51216ALL.pdf) with an AS7C4098A-12 (https://au.mouser.com/datasheet/2/12/as7c4098a_v1.2-1288279.pdf), as the latter has much ...
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3answers
416 views

True 5V CPLD other than PIC/Altera ATF150*?

Are there any True 5V CPLD's families still in manufacturing other than PIC/Atmel ATF150*? I am talking not just "5V tolerant IO", but rather ones with 5V VCCIO, able to drive 5V loads without ...
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0answers
135 views

Are pull-up resistors mandatory for inputs on modern parallel ports?

Here I go again testing more circuits on two computers with each reporting completely different data yet I feed the same data in. Now this time, the data coming back is all logic highs on my laptop ...
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1answer
165 views

TTL NAND logic circuit

how can find the maximum fan-out of the TTL-NAND gate using LTSpice ? i tried to solve problem by hand, but the problem how to find fan-out using ltspice