Disc reader project -- quick status update

Keith M keithvz at verizon.net
Wed Dec 9 13:34:53 CST 2009


Al Kossow wrote:

> There is no need to record every value if it is only a binary signal, you
> can store the delta time to the next transition.

With my current implementation, I take that one step further, and 
process the delta T's within the hardware, to see if they fall in a 
particular range, and then store this equivalent RAW MFM data in the 
memory.  And then transfer contents of memory (once bit aligned with the 
sync word, also in hardware) via USB to the PC.  I understand where 
having the raw delta T's inside a PC/or something with more power, makes 
sense.

> This is the difference on
> a logic analyzer between 'state' and 'timing' modes. In 'state' mode, you
> sample and save every signal at each event. In 'timing' mode, a high 
> resolution
> clock is used to measure the durations of each signal.

My (limited) understanding was that timing mode you used a clock source 
internal(ie local oscillator) to the logic analyzer to determine when to 
sample --- it not synchronized with the DUT.

And state mode was an external clock, synchronized with the clock 
present within the DUT, which told the LA when to sample.  At least 
that's how I understood it.

This is how I've used both my LAs...

Thanks

Keith




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