Em 4/3/2011 16:36, Dwayne Reid escreveu:
> Good day to all.
>
> I'm tackling another project where I need to intercept a SPI data=20
> stream and modify the data on the fly.  I'm only interested in=20
> modifying the data feeding a pair of 74hc595 shift registers but the=20
> SPI buss is used for talking to lots of different devices.  There is=20
> a separate Latch line that latches the data into the two shift=20
> registers at the appropriate time.
>
> So: I have to continually buffer two bytes worth of data until the=20
> Latch line becomes asserted.  I'll then modify the data and spit it=20
> out to the shift registers.
>
> I haven't even put a scope on this beast yet to see how fast the SPI=20
> data is but I suspect that its pretty quick - there are a lot of=20
> devices on the buss that are updated in real time.
>
> Although my first thought was to use a PIC that can do hardware SPI=20
> slave, I'm not sure if its fast enough.  I'll find out later today=20
> when I put a scope on the SPI buss.
>
> Assuming that the PIC isn't fast enough, my next thought was to use a=20
> small CPLD.  Therein lies my problem.
>
> All of my CPLD experience is with old Intel / Altera parts: ep320,=20
> ep610, ep910, epm7032, epm7128.  The last of those projects was=20
> around 15 years ago and written in Altera's Advance Design File or=20
> Text Design File formats (.ADF, .TDF).  I have no experience with=20
> Verilog or VHDL.
>
> That's the software side.  The hardware side is also a little=20
> challenging: the SPI buss and those shift registers are running from=20
> 5Vdc.  Most modern CPLD's seem to be 3.3V or lower.
>
> So: I'm looking for suggestions for a small to medium size CPLD that=20
> runs at 5V and has at least 40 macrocells.  I can probably get away=20
> with fewer macrocells (as few as 24) if I generate the output data on=20
> the fly (rather than loading a 16-stage shift register and shifting=20
> the data out) but I'd have to see how flexible the product term array=20
> is for that kind of thing.
>
> I'd appreciate any suggestions or opinions that others might have.
>
> Many thanks!
>
> dwayne


Altera's MAX7000S series supports 5V I/Os, MAX3000 series have 5V
tolerant I/Os.


Best regards,

Isaac

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