Questions tagged [clock-speed]

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

Filter by
Sorted by
Tagged with
8
votes
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. ...
16
votes
2answers
8k 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?...
2
votes
1answer
927 views

Determine suitable clock speed?

I want to learn about good techniques on how to choose the suitable clock speed for the microcontroller for a project. For example i want to create a device with a pic16f877 microcontroller that ...
2
votes
1answer
353 views

Limitation of baud due to propagation of voltage over distance

I need to make sure I have my facts straight here; the math works but I may be missing something: In a 100BaseTX network over Cat-5 copper, each party has a circuit (one twisted pair) on which they ...
5
votes
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
votes
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 ...
9
votes
1answer
483 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 ...
4
votes
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 ...
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 ...
6
votes
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 ...
2
votes
2answers
917 views

Clarification on what the max freq of PIC24FJ64 is?

I'm confusing myself a bit here. The following is taken from this datasheet: High-Performance CPU: Modified Harvard Architecture Up to 16 MIPS Operation @ 32 MHz Now I want 16 MIPS, which is its ...
33
votes
3answers
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, ...
2
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 ...
1
vote
2answers
5k views

ADC sampling rate to MCU clock speed relationship

How can I determine the clock speed requirements of a mCU to manage a given ADC input? This application is very simple - I just want to take an SPI stream from an ADC into a mCU and spit it out the ...
12
votes
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 ...
9
votes
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 ...
0
votes
1answer
230 views

bit bang programming with a 1/222.2ns clock

I need to bit bang at a 1/222.2ns clock rate. I am looking a recommendation for the bit banging clock source and "easy" to program means of bit banging at this clock rate.
8
votes
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 ...
7
votes
2answers
27k 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 ...
17
votes
7answers
35k 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 ...