Re: help ...!!!

Hash wrote: 
well dudes ya making fun of me or wat ever .. any how jerry if ya so
serious about ya language then i can have ma chance and i can ask
question in ma own language from ya .. and ya whole 7 generation can
not answer that got it dear so .. stop such things....

and if ya know something why ya do not help me .. justmaking fun of me
.. well ahhhh
any how BHASKAR plzz answer ma question which i asked ya in the aboove
posts ...

take care

If you want an answer from the members of this newsgroup then you should follow their requests and use proper english.

To put it bluntly, you sound like a punk, and no one likes to help punks.

There are many different 8051 variants available, all of which tend to run on different clock speeds, and have different timing specifications.
In addition to the absolute maximum frequency measurement limit imposed by the actual hardware, you will be limited by the software that will be running on the micro. If additional processing time is taken up then this will decrease the maximum frequency measurement.

The maximum frequency for the simplest software, will involve the time taken to simply read the input pin, then to read it again.
You will ofcourse require additional logic, such as storing the previous pin value, and then checking the new value to match the old one etc, which will slow down the process.

Alternatively you may use an interrupt (on a pin state change) and a timer, you would then need to calculate how long the interrupt takes to execute, and thus how often they can occur without overlapping. This would be your minimum time period, and hence would give maximum frequency.
.

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