Questions tagged [clock-speed]

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

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34
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8k views

Why do Arduinos ship w/ 16MHz crystal instead of 20MHz?

Why do Arduino boards ship w/ 16MHz crystal instead of 20MHz? They are spec'ed for operating at 20MHz, after all. I guess there are a few advantages to running more slowly (lower power consumption, ...
26
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3answers
7k views

How is 255 Tbit/s processed in optical fiber communication?

I have never understood how the new record breaking data transfer speeds are achieved in terms of converting from/to electrical and optical signals. Suppose we have 255 Tbits of data and we want to ...
22
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4answers
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 ...
18
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7answers
37k views

How do I set the clock speed fuses on an ATtiny85 when using an Arduino as a programmer?

I'm following this tutorial, programming the ATtiny85 with an Arduino, using it to play some tones (through a piezo speaker). I'm struggling with getting the tones at the right pitch (I'm creating the ...
16
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2answers
9k views

How can a CPU dynamically change its clock frequency?

My Intel CPU changes clock speed depending on the usage, but how does it decide what clock speed to run at? Is the clock speed determined by the OS software using an algorithm, or is it hardware based?...
12
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5answers
5k views

“Overclocking” an AVR

In AVR datasheets under the Electrical Characteristics section you will typically find a graph like this (this one is from the ATMega328): I've seen designs that seem to "work" but operate outside ...
10
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2answers
16k views

What generates the clock signal in a fast CPU and how does it work?

Often, for integrated circuits, a quartz crystal is used to generate the clock signal. However, this only reaches speeds in MHz. What component, or what circuit, generates signals up to 5 GHz ...
10
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2answers
7k views

Maximum clock frequency of microprocessors

Recently, I have heard that AMD has released the new Vishera series of FX processors which run at 5 GHZ. My question is whether there is any upper bound of clock rate of a processor? That is can we ...
9
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5answers
2k views

Does anyone know of a microcontroller/DSP with no clock speeds or any oscillators in excess of 1.705 MHz?

I am planning on making a simple electronic device which I might eventually try to market if it works out O.K. Before taking the plunge and trying to mass produce it, I would first try to sell a few ...
9
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3answers
6k views

Can faster processors/clocks execute more code?

I am writing a program to run on an ATmega 328 which runs at 16Mhz (its an Arduino Duemilanove if you know them, it's an AVR chip). I have an interrupt process running every 100 microseconds. It's ...
9
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1answer
506 views

Is a 10GHz clock required to drive a 10Gb serial pin?

I am reading about the 10Gb/s Ethernet PHY for Altera FPGAs (datasheet here). I was impressed to know that, at the hardware level, the 10Gb/s is done serially. Naively, I would think to do 10Gb/s ...
8
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2answers
1k views

Does a baudrate in serial communication (USB or RS232) need to be exact?

In serial communication, does the baudrate mean we have to use the exact clock speed or is it a range of speeds that we can use? and if it's an exact value, how exact should it be ? for example, can ...
8
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2answers
7k views

AVR interrupt service routine not executing as fast as expected (instruction overhead?)

I'm developing a small logic analyzer with 7 inputs. My target device is an ATmega168 with a 20MHz clock rate. To detect logic changes I use pin change interrupts. ...
8
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1answer
8k views

HSI and MSI - Applications of two Internal RC OSC in Microcontroller

In a ST microcontroller I'm using there are two OSC's that can be routed to exactly the same hardware and I'm wondering when you would use each one. Link to part documentation STM32L496ZG Excerpt ...
7
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4answers
656 views

Exotic semiconductors for fast digital ASIC

I am researching exotic semiconductors for a digital ASIC with a few million logic gates which should run as fast as possible within a $30 million budget. (Specifically, I need to do a single fully-...
7
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3answers
29k views

How do I calculate needed pixel clock frequency?

If I want to have a resolution of X * Y pixels, updating in frequency f. How do I calculate the pixel clock speed? Example: 1280 x 1024 @ 85Hz usually have a pixel clock of 157.5 MHz, but how do I ...
7
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1answer
615 views

pic32 maximum external frequency while running from internal 8MHz RC oscillator

I am completely new to PICs and I have never worked with a part as complex as this. In particular, I'm wondering if it is possible to generate a reference clock (REFCLKO in the datasheet) at 11.2896 ...
6
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5answers
4k views

Why are DIMMs not equipped with a heat sink like a CPU?

I know that a DIMM is composed of a set of chips that contain control logic managing the decode and prefetching memory operations. According to a product specification, I found that newer RAM works at ...
6
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4answers
3k views

Increase Microcontroller frequency and Speed

I am in process of upgrading the micro-controller of our project from Renesas M16C to RX63N. In our current M16C project we use 16HMz crystal. If in the new micro-controller Rx63N if I use the ...
6
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5answers
1k views

Relationship between I2C drawn energy / power consumption and data rate

Referring to just what the I2C lines draw, am I wrong thinking that the higher the clock frequency the shorter the time there will be (the same amount of) current flowing through the pullups and thus ...
6
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1answer
3k views

STM32F4 : Floating point instructions too slow

I'm working on an audio application on the Nucleo F411RE and I've noticed that my processing was too slow, making the application skip some samples. Looking at my disassembly I figured given the ...
6
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1answer
2k views

Is CPU/GPGPU heat dissipation quadratic in clock frequency?

In the following article on overclocking a Pentium from 1GHz to 5GHz using liquid nitrogen: The 5GHz Project, there is an assertion that "Heat dissipation rises exponentially during extreme ...
6
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2answers
668 views

Nanosecond interrupt accuracy on a 64MHz microprocessor

I am currently designing a PCB with a 64MHz nRF52832 bluetooth MCU. I have an interrupt connected to this MCU which needs to be detected with 1-3 nanosecond accuracy. Unfortunately, the 64MHz MCU has ...
5
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4answers
2k views

Is there a small (6-pin) DIP I can use to generate multi-MHz squarewave clocks with an external crystal?

I'm building a circuit that I'd like to run at 8 MHz to begin with, but I want to be able to try it out at 10, 12, 16, 20, and, maybe, 25 MHz. I know that many microcontrollers have the ability to ...
5
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3answers
3k views

What does an MCU need to be capable of USB 3.0 communication?

USB 3.0 has been around for quite some time, since it was released in 2008. But you don't see any simple microcontrollers with an internal peripheral that can do USB 3.0. The Atmega32u4, a simple ...
5
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3answers
4k views

How do I know if my microcontroller clock frequency is fast enough?

I've been using ARM microcontrollers from NXP in commercial products with great success for the last 2 years. In most of my projects I don't use the PLL to increase the oscillator frequency because ...
5
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3answers
36k views

How to calculate the time of one single tick on microcontroller

I have been in Embedded system for 8 months. I have worked application part more compare with low level. I have basic questions on systems ticks, How to calculate the system tick of Timer, if I am ...
5
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2answers
423 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.
5
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3answers
5k views

PIC problem: Touching the crystal capacitor makes the system slows down

I am experiencing a very unusual problem (at least for me). When I touch with my fingers, or the oscilloscope probes, on the crystal or it's capacitors, the PIC runs slower...and A LOT slower then it ...
4
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3answers
4k views

How to measure Clock frequency of PIC?

I am using PIC micro controller (PIC16F1846) with an external 8MHz crystal attached to the external clock pins (RA6 and RA7). Why is it that when I use my oscilloscope probe to attempt to measure ...
4
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3answers
1k views

ATmega - Why is the prescaler factory defaulted to 8?

Why do ATmega (e.g. 328P or 644P) have CKDIV8 (or CLKPS = 0011) factory programmed along with a default internal 8 MHz ...
4
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1answer
571 views

What kind of use cases require a 2GHz, 4GHz, 6GHz, 30GHz or 100GHz oscilloscope? [closed]

I have been thinking of buying some oscilloscope for the work I do with Arduino. In my case it would be partly because of some usefulness and partly because it would give me a chance to learn an ...
4
votes
1answer
411 views

Pull up resistor in NMOS logic value

For my senior high school project I decided to build a basic CPU from discrete components. I plan on using a 5V logic level and the current design calls for around 2000-3000 N-channel MOSFET ...
4
votes
4answers
681 views

Is Transmission Line Reflection Frequency Dependent?

I'm currently sending high speed serial over a coax cable. I've got an oscilloscope hooked up (on the load end) trying to watch the clock pulse signal. I've got a 10 ft coax cable with a 12.5 Mhz ...
4
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5answers
2k views

Can't run PIC24EP128MC206 at rated speed

I got a PIC24EP128MC206 because of its rated speed of 70 MIPS. (For whatever reason, it is rated in MIPS, while most other PIC24s are rated in MHz.) Since my understanding is that one instruction on ...
4
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1answer
3k views

Why ATMega328 can't run SPI at full clock speed

Two part question: In the datasheet on page 168, the best SCK frequency one get get on SPI is \$\dfrac{f_{osc}}{2}\$, why can't this be \$f_{osc}\$? Also from the datasheet: "When the SPI is ...
4
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3answers
2k views

Clock skew? Good or bad?

So, I've been reading up on clock skew. I came across the fact that clock skew can be incredibly useful, in the sense that positive skew can be used to speed up the circuit by increasing the clock's ...
4
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0answers
121 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 ...
3
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4answers
3k views

Is a 4/3 clock divider possible?

I have seen designs for digital clock dividers, which can divide a clock frequency by 1.5, 2.5, etc. But is it possible to create digital logic which divides a clock by 4/3? For example, if I have a ...
3
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5answers
10k views

How to check PIC system clock speed MCU?

The entire project depends on this, so I just want to make sure I have it right. I'm using a 20MHz external resonator and putting that through the PLL in hopes of getting an F_SYS = 120MHz. Without ...
3
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2answers
1k views

Why do micro controllers run @ 100's MHz whilst CPUs run @ GHz? [closed]

Whoopie - I've got a Raspberry Pi. When doing stuff it runs @ 1.2GHz and there are Uber overclockers out there who have boosted them to 1.5GHz (with phase change coolers). Today, the cheapest CPU on ...
3
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2answers
2k views

Microcontroller requirements for TFT display

I want to know if I can drive this 320x240 TFT display: http://www.buydisplay.com/download/manual/ER-TFT032-2_Datasheet.pdf Which has this controller built-in with 168KB dedicated RAM: http://www....
3
votes
1answer
1k views

What is my AHB1 clock rate?

I am working with an ARM Cortex M3 chip (reference manual available here). I'm trying to get the baud rate of my USART communications right. Reading pages 613 onwards, I understand that the value I ...
3
votes
2answers
1k views

RPi GPIO speed issue in bare metal

After reading the excellent article on bare metal by David Welch (https://github.com/dwelch67/raspberrypi/tree/master/baremetal), a friend and I are trying to implement a simple GPIO toggle. It's ...
3
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2answers
2k views

How to check frequency of MSP430 clock?

I'm working on a project in which an MSP430 is used to provide the timing for some stuff where accurate timing is important (it can be off by 10%, but not by 2x). This is driven by the timer A0 ...
3
votes
2answers
711 views

CPU and clock rate

As I understand it, CPUs generate electrical pulses using a quartz crystal. The rate the pulses are generated (taking into account various multipliers) give the processing speed which all components ...
3
votes
1answer
15k views

Multiplex Seven Segment Display Fast enough to make Solid

I have been trying to multiplex a 4 digit seven segment display on my FPGA board but have been running into not being to get it fast enough so it looks solid to the human eye. You can see an example ...
3
votes
1answer
144 views

Quartz Clock Accuracy

Do the vibrations of aircraft engines (or any engine, for that matter) dilute the accuracy of a quartz clock? I haven't done any kind of research or hypothesis testing, though I believe that the ...
3
votes
2answers
842 views

How to set external clock value for STM32F1?

I creating a project with the microcontroller STM32F101C8t. This microcontroller has an internal clock of 36MHz. My question is how to correctly set the external clock value, ie what crystal value ...
3
votes
2answers
670 views

Problem with connecting clock divider generated by CORE Generator to I2S design for Spartan 6

I'm trying to connect clock divider generated by CORE Generator to I2S receiver and I2S transmitter on Spartan 6. The PLL_BASE is connected via ODDR2 module, as adviced. Both receiver and transmitter ...