Questions tagged [clock-speed]

Anything related to clock signal frequency (a.k.a. clock speed) issues in digital systems.

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SPI bus termination for variable line length / variable number of slaves

There is a lot of information online for SPI bus termination, but my situation is a little bit different. I have created a system with the intention of 'plug and play' IMUs. Although the main ...
0 votes
3 answers
110 views

Why can't you use any clock speed with an Arduino?

So if every IC is made of transistors what stops me from putting a ATmega328 on a breadboard with a 20 MHz clock so it will run faster? This is a rhetorical question. I don't need to know how I could ...
1 vote
1 answer
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ATMega32u4 minimum system clock for USB 2.0

I am trying to cut down the power consumption for an ATMega32u4. The datasheet says, for USB 2.0 it needs an external clock, which it uses to generate a 48 MHz clock by multiplying the external clock ...
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2 answers
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Why didn't cpu clock frequency plateau at two orders of magnitude higher Hz?

Here is a back of the envelope estimate for an upper bound of clock frequency for modern CPU's: The speed of light is 3·10⁸ m/s which is 3·10¹¹ mm/s, and I assume the speed of electricity is about 50% ...
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1 vote
1 answer
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Minimum FPGA clock frequency

I currently work with two FPGAs, Microchip/Microsemi ProASIC3E and AMD/Xilinx Zynq-7020. In their datasheets, the recommended minimum operating frequency is 1.5 MHz for the A3PE ProASIC3E chip. The ...
3 votes
1 answer
88 views

Rise time and clock frequency: when does it start biting me?

I have spent quite a bit of time reading (mostly the questions and answers on here) about rise times of square waves and how they can cause transmission line effects (reflection, ringing, etc.). ...
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1 vote
1 answer
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STM32F303RE Nucleo freezes at clock rate >40MHz

I have a STM32F303RE Nucleo board with Mecrisp-Stellaris Forth. The Forth console goes through USART2, the interface connected to the ST-Link part of the Nucleo board (changed from default USART1). ...
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0 answers
176 views

How do I change and verify the clock frequency of Atmega4809 microcontroller? CLKOUT not working?

In the below code I am trying to get the clock frequency to show up on the CLKOUT pin which should be pinA7. But for some reason I don't get anything when measuring pinA7 on an oscillicope. I do see ...
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2 votes
2 answers
65 views

Self programming fails on ATmega2561

We've been programming a custom Board with an ATmega2561 via a serial (RS232) connection for years, mostly without problem. We're using a custom bootloader that is closely based on recommondations in ...
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2 votes
1 answer
268 views

How to constrain a source-synchronous FPGA input?

I have a source-synchronous input to my FPGA (an Intel Cyclone 10 GX 10CX085), coming from an external chip whose datasheet gives the following information: fmax = 300 MHz (single data rate) tsetup = ...
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0 votes
2 answers
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Why will clock signals have different phases after a frequency divider?

I have a question about data transport between two chips with series format. I have two chips. Chip 1 will sent 8-bits data to chip 2. The picture shows a solution. I will provide a 100MHz clock from ...
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0 answers
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How to manipulate timer registers of Arduino Uno?

I already asked about How to achieve high speed microstepping? I even used Arduino Due to achieve high speed. Practically there was no difference compared to Uno but by changing baud rate I could see ...
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1 vote
2 answers
165 views

Digital circuit to compare clock frequencies

The task I am trying to do: Design a digital circuit that takes in two clocks at different frequencies and finds the higher frequency clock. Eg: Say clk0 = 10MHz and clk1 = 5MHz and clk0 is given to ...
1 vote
2 answers
100 views

SAM3x8e can't program over serial

UPDATE: Jan 2022. I put together a new pcb. This one has the JTAG header and I have an ATMEL-ICE. Otherwise the processor and support layout is mostly the same. I stripped the program down to simply ...
10 votes
4 answers
3k views

How does the current processor technology with low clock rates (<10 GHz) deals with mmWave (>10 GHz) technology used in 5G?

What I mean is that most abundant computing processors in market have the clock frequencies in the range of 2-4 GHz and from wikipedia: As of 2012, the CPU-Z record for the highest CPU clock rate is ...
0 votes
1 answer
99 views

For a clocked circuit, what defines how fast the clock can be?

Imagine a typical PCB that's small, 6" per side. There's a clocked circuit on it. Making a 1kHz circuit is pretty easy. Making a 2kHz circuit isn't any harder, and neither is a 3kHz circuit. ...
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2 answers
155 views

What does clock/signal speed actually do?

This is may be a silly questions but I am curious. I know that in circuits power lines are at speed near light but why are signal lines so different? Let's say I use I2C(MCP23017) I can choose between ...
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1 vote
2 answers
263 views

What refresh rate do digital stopwatches use?

We've all probably come across these kinds of electronic stopwatches at some point: They almost always claim to count centiseconds (although this one counts in milliseconds), but do they really have ...
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1 answer
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What is the difference between the switching speed and clock speed of a chip [closed]

I learnt that the switching speed of Silicon-based devices are in the KHz range whereas that of III-V semiconductors like GaN are in the MHz range. How does this differ from the clock speed that we ...
1 vote
3 answers
406 views

How are system clock and oscillator frequency related?

My question is given a, for example, a quartz oscillator on a MCU board, how is the system clock generated? I'll break down this question into several parts below: I always have the impression that ...
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2 answers
387 views

Do all SDRAM applications require high-speed routing?

I am a chemistry student and I am beginning to realize that I have fallen into a EE rabbit hole.. I am trying to create a PCB (digital audio delay unit) from a schematic which includes a SDRAM, this ...
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2 answers
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Clock signal frequency [closed]

If the longest path that my digital signal must travel in a microprocessor is x cm. What would be the highest frequency of the clock signal for that chip?
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Why the assembly code does not match the number of cycles of ARM M4?

I ran the following C program on STM32F405 (ARM Cortex-m4). I tried to comprehend its computation period instruction-by-instruction. ...
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2 answers
510 views

How to derive an exact 10Hz clock from the generated clock?

How do I go about getting an exact (or as close as possible) 10Hz clock from the generated clock? The master is 100MHz. I have used this 32-bit register to make a clock as close as possible to 10kHz ...
0 votes
1 answer
416 views

ATMEGA328P Max Clock Speed Without Divider

Does anyone know what the max clock speed of the ATMEGA328P is, without the clock divider? I know that people have been able to overclock the 328 to 30 - 50 Mhz, but I haven't found if those are using ...
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1 answer
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How to create a delayed clock pulse, then return to regular clock cycles

I am attempting to configure an LCD with just IC chips and I've been having problems. I've worked out that the main problem I am having is in the initialization of the lcd. It needs a goodly amount of ...
0 votes
2 answers
102 views

FPGA Data Collector - What Specs Should I Look For? [closed]

I'm working on a high-speed data collection device for an ADC running at 80 Msps. After digging through resources on MCUs and asking several questions here and in other forums, I've turned my ...
1 vote
1 answer
344 views

STM32F407 Clock Configuration Order

I have been taking a Udemy course on the STM32F407 and using the Discovery board to go along. However, clock configuration is not covered in the course. After some Googling and nose in the reference ...
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3 answers
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What's the difference between the maximum and cut-off frequencies of a single transistor compared to those of a circuit? [closed]

Many publications, when they speak about a single transistor, the maximum and cut-off frequencies are way higher than of the final circuit. Example: A modern FinFET, some report a maximum oscillation ...
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-1 votes
1 answer
351 views

STM32F407VG Discovery + CMSIS HSE Clock Configuration

I am trying to program an STM32F4 discovery board using Vscode, Platformio and CMSIS. However, I cannot set the right clock frequency. I have programmed it to blink an LED every second, except it ...
0 votes
2 answers
155 views

Gigabit transceiver with MHz reference clock

I've some experience with Xilinx FPGA generating 10Gb/s over SMA loopback with on-off keying modulation (what scope shows) to perform BER test but the documentation shows it uses a reference clock in ...
0 votes
1 answer
307 views

UART does not work properly after changing HSI to MSI in STM32L152

I am using STM32L152R8T6-A MCU. I use 3 UARTs in my project. UART buadrates are 9600 and 115200 bps. Initially I set the clock source to HSI (16MHz) and everything worked fine. But then I decided to ...
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1 vote
0 answers
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How to set SPI clock speed for MT7623N

first I must say, I am new to the HW programming, but I really enjoy it. My first project is writing a library for MT7623N (BananaPi R2) that handles GPIO pins. I got the GPIO part done and I can set ...
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1 vote
0 answers
44 views

Impact of reduction on Dynamic energy and dynamic power in microprocessors

A microprocessor has been designed to have a dynamic switch which reduces power consumption when the loading reduces. Assuming a reduction of 20% in voltage reduces clock frequency by 20%. Calculate ...
1 vote
1 answer
62 views

Unexpected Behavior: i2s L/R clock only works under arbitrary conditions?

I'm new to Verilog (and HDL at all) and working with a Cyclone II EP2C5 Mini Dev Board in Quartus II (version 13sp1 to be compatible with my cheap FPGA). I use the below two modules (one mostly just a ...
1 vote
1 answer
280 views

How to change the clock frequency of a STM32H753ZI

just got a new MCU for testing and having a hard time changing its clock speed to the maximum (480MHz) Using bare metals or directly manipulating the registers as I never liked the HAL interface. What ...
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-1 votes
1 answer
237 views

What is Symbol Clock Frequency?

I came across the term Symbol Clock Frequency in this Intel programmer reference manual (P131). I could not find what the symbol clock frequency actually is in the manual or online and thought it ...
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6 votes
2 answers
2k views

Ways to observe clock signal of an STM32 MCU

Is there a nice way to be able to observe the clock signal in an oscilloscope to validate my settings for clock speed? After setting it to 168 MHz with PLL for an STM32F407VGT6 MCU let's say.
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1 vote
1 answer
1k views

Find critical path and maximum clock frequency in digital circuit

I have this problem: Consider this circuit: Find and describe the critical path. What is the maximum clock frequency? MY ATTEMPT Okay, this is how I see the critical path: DFF -> G1 ->...
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1 vote
1 answer
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Oscillator slows down when my hand hovers over it

I'm teaching myself VHDL using this MAX II CPLD board. I designed a frequency divider and 4-bit counter in VHDL using the onboard 50MHz oscillator. It seemed to work as the onboard LEDs are flashing ...
0 votes
1 answer
973 views

Calculate C and R in a CMOS Crystal Oscillator

I stumbled over this simple solution to drive a crystal oscillator, but I need to connect a 25.17MHz crystal instead of the 10MHz in this schematic. How do I calculate R1 and C for a given frequency f(...
1 vote
1 answer
396 views

How to synchronize PIC PWM clocks?

I'm considering a design which has multiple PIC-based controllers producing PWM signals at 31 kHz. Sometimes, under a well-defined "handover" condition, some pair of PWM power feeds will be connected ...
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1 answer
427 views

WAVGAT Pro Mini, no serial output

I ordered some Pro Minis however get some WAVGAT clone thingies. The first problem was it is running too slow (4x slower) when compiling with default "Pro or Pro Mini" board profile. Serial however ...
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-3 votes
1 answer
476 views

How to compute clock cycle time from given frequency

let's say I have a processor runs at 100MHZ frequency how can I compute from this it's clock time for each cycle? I know that Frequency = 1 / Clock Time but I am having trouble to fully understand how ...
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3 votes
0 answers
473 views

Increasing system clock frequency on STM32F303 drops I2C clock proportionately - why?

I'm trying to figure out a weird little issue I've discovered while debugging another element of my code. I've got a STM32F303K8 reading and writing to an I2C peripheral. The I2C clock speed is ...
22 votes
5 answers
4k views

How to communicate faster than the system clock

I was reading about the new (ish) Thunderbolt 3 today, and was very impressed by the specced speed of 40Gbps. Then I looked at Intel's latest i9 processor speed... about 4.2GHz max. How can a system ...
4 votes
0 answers
247 views

ATTiny85 clock speed problem

Using an ATTiny85 and an Arduino loader I created a simple device for turning on an exhaust fan based on a light sensor. The ATTiny85 turns on the fan after activating a warning light and sounding an ...
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1 answer
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How to set up clock for the STM32 Nucleo-64 with libopencm3/rtos

I was using this code from github on a blue pill. Now I would like to adapt it for STM32F401 on a Nucleo-64 board. I tried changing the GPIO to A7 and attaching an led (which lit up when I attached it ...
0 votes
1 answer
148 views

How can I create a long (10 second) pulse from a short active pulse?

So let's say I have an incoming signal: 1 clock cycle from a ~1-100 MHz (50 MHz for this example) clock domain. And I want to drive an output that must be active high for 10 seconds for each time the ...
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Clock Generation from Oscillator

Is there specific standard ways to generate clocks from oscillators? Referring to generating a square-wave clock from a sinusoidal oscillator output. I can think of a few circuits involving diodes as ...

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