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use of built in clock of the computer to generate fixed clock frequency to measure the period of a signal on dte terminal of rs232 using labview6.1 version

want to develop a very high frequency measument technique using labview6.1 version i'm equiped with rs232 port where the signal frequency to be found is given on one of the control lines and is compared using the internal clock of the system please help me in finding hw to access internal clock of the system in labview 6.1 version
thanking you in anticipation
sridhar
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Sridhar,

I do not think you will be able to do what you are asking. The OS controls the serial port hardware. If the UART has its own oscillator, then you have two clocks which are not synchronized to deal with. I have never seen any method of accessing either clock form within LV. Further, since RS-232 is an asynchronous communications method, timing is not defined beyond the frame of one byte.

Perhaps if you described your measurement problem in more detail, someone could offer a solution. Information we would need include: minimum and maximum frequencies, waveform and amplitude, accuracy and resolution, how often are measurements required, and anything else you think might be relevant.

Lynn
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lynn,
sir thanks for replying i think i was not clear with my question i would like to
reframe my question i'm woking on rs232 and labview,i made a square wave on one the
control terminal(as RTS etc.), other than Rx & Tx.(i made an LED button on front panel glow
according to signal on rs232). so i think there is any thing to do
with UART or asyncronous transmission. now all that i want to do is just measure the
number of pulses in a particular duration of time as the inverse of that gives frequency
all that i want is how to get this specified time. i think it would be better if at all the
specified time interval is a variable that is measure number of pulses in 1sec, .1 sec. .01sec
etc, so tht if at all frequency is very large and varying i can track it also
thanking you in anticipation
regards,
sridhar
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Sridhar,

Software timing is never very accurate because of the uncertaintites the operating system introduces.

Given that warning, here is something that might work. You could monitor the RTS in a loop and increment the value of a shift register every time the signal cycles. Also monitor the Tick count compared to the start tick count. When the tick count difference matches the meausrement period, read the shift register count and reset it to zero for the next measurement.

Lynn
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