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frequency and time calculation

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Jononomous

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So the equation for calculating frequency is E/T = F ... E is the number of events (in this case binary pulses), T is the time in seconds, and F is the frequency in hertz. So my question is... using the formula above we get T = E/F.

With that said:
8pulses/200000hz = 40microseconds(us)
8pulses/4000hz = 2milliseconds(ms)

So to get the same rate using 4Mhz, I would have to do the following:
200/4 = 50x faster

So that means we have to convert .00004s to 50x slower via:
.00004/50 = 0.0000008s

So to have the same pulse rate at 200Mhz from 4Mhz, I have to move 50x faster...

Is my thinking correct?

Basically I want to achieve the same pulse rate using two different frequencies... so what would the time factor be to go from 4Mhz to 200Mhz?

Also, what would the disadvantage be to using a 4Mhz crystal to accomplish this rather than say a 25Mhz crystal? Any Disadvantages?
Trying to pin down really how binary signals are transmitted through analog... don't quite understand the circuitry behind it... do I place the MCU inline with the output line and just generate pulses?

Thanks guys!

Edit: Any now that I look at my MCU specs... The max pulse width is 2us so how on earth would I generate a 8.0x10^-7s pulse?
 
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Pulse rate is pulses/second, which has the same units as frequency (i.e. cycles/second or Hz).

So what is your question?
 
Well if a 4Mhz internal RC can't handle a pulse generation of 8.0x10^-7s to match the required pulse at 200Mhz... what would I use to generate a pulse that quickly? A 555? External clock? If my PIC can only drive a pulse at 2us (at the fastest), how would I generate a pulse at 8.0x10^-7s? (Perhaps an external clock on that IC to better match the timings; but then how would I generate the pulse that fast?)
 
Do you need a generate a fixed frequency of 1/(8x10-7) = 125000 Hz? What does that have to do with 200MHz?
 
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Well I'm trying to match the pulses off a remote control toy, I can see them briefly (very briefly) on the oscilloscope... but have no means of recording the pulses. Frequency counter says its around 200Mhz ... but obviously I don't have a 200Mhz crystal... so how do I generate pulses that equal the ones being generated at 200Mhz?
 
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Chances are that the toy is using an RF carrier that is being modulated (either OOK or FM) by some data pulses, sort of like the pulses that are used with IR remote controls. You can do what is being done inside remote control for the toy; use a one-transistor oscillator, or a crystal controlled oscillator as the RF transmitter, and use a digital circuit (PIC?) to generate the modulating pulses. That way, the PIC isn't required to deal at all with RF frequencies.

btw, I doubt that the signaling is being done at 200MHz; that is not one of the license-free remote control frequencies.
 
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But don't the pulses have to match the frequency in order to be the correct pulse width? I would be using the PIC as you stated, but if the pic can only generate a 2us pulse width as its fastest pulse at 4Mhz, how would it generate one at 200+ Mhz? Or is it that the pulse itself doesnt matter, it's just the frequency the pulse gets sent to? So IE: if i had a line pushin like 500mhz (theoretical), and generated a pulse with the PIC... it would be a pulse at 500mhz correct? Or would it only be a pulse at the 4Mhz coming off the PIC?
 
More likely, the command pulses are very slow, like ms or 100s of usec. The modulation pulses do not have to be synchronous with the RF carrier; they just turn on/off the RF carrier.
 
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