Re: EDD + CARD

[Stephen Shaw <bottrawler@junkbuster.zzn.com>]

On 01 Aug 2002 20:27:37 GMT, Michael J. Mahon wrote:

> Matthew Russotto replied:
>
>>In article <20020731195944.08453.00001107@mb-mq.aol.com>,
>>Michael J. Mahon <mjmahon@aol.com> wrote:
>>>
>>>With the bit stream at 250,000 bits per second, that seems unlikely.
>>
>>I thought so initially, but maybe not.  With external clocking, some
>>serial ports might be able to handle that.
>
> If the clocking is external, then the purpose of synchronizing to the
> asynchronous "start bits" in the data stream is defeated.
>
> If an external clock is used to put the USART into synchronous mode,
> then Nyquist requires that the bit sampling rate be at least 500kbits/sec
> to recover the data unambiguously, if the pulses were 50% duty cycle
> (which they are not).
>
> This would be easier to do with a serial-in/parallel-out shift register
> interfaced to a parallel port.  Again, the shift clock would have to be
> high to capture the pulses, but at 2MHz, the shift register would fill
> in 4 microseconds, which is not too fast for a parallel port to read.

I'm too snowed under at the moment - David Wilson are you listening? :)


>
> -michael
>
> Check out 8-bit Apple sound that will amaze you on my
> Home page:  http://members.aol.com/MJMahon/

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