Re: need small PAL with SR latch

"Joel Kolstad" <JKolstad71HatesSpam@xxxxxxxxx> wrote in message
news:11bob0f3t3k37bf@xxxxxxxxxxxxxxxxxxxxx
> "colin" <no.spam.for.me@xxxxxxxxxxxx> wrote in message
> news:dOVue.4085$BD2.1932@xxxxxxxxxxxxxxxxxxxxxxx
> > I need a small prgramable logic device with a couple of SR latches,
> > however they all seem to have D types or other type of latch on the
macro
> > cell with a global clock/set/reset, exept for some of the realy big
ones.
> > Ive looked through all of the ones that Farnell sell, and although I
> > could obviously feed back an output to make an SR latch this wouldnt be
> > ideal, any one know if there are any like this ?
>
> Why do you say that feeding back an output (internally within the part)
isn't
> ideal? With most of the smaller PLDs, the routing is pretty
staightforward
> (and fixed!) so it's reasonable to just build your own using the AND-OR
array
> within the part.

I estimate there would be 6 gates in the circular path as well as the
loading of the output pin and grid lines, compared to a normal latch etc
were there is a circular path of 2 gates with minimal loading. there would
be a significant diference in speed/generated noise. Im trying to acuratly
measure relative edge timings so the faster the better, bit like in a type
II phase detector, except I found that doesnt work quite the way I expected
as it is indeterminate if a waveforem is 90' or 270' out of phase. a simple
xor detector would not alow as much sensitivity.

>
> > Only needs a dozen gates or so to do the job, could do with being
fast
> > as posible and in circuit programable etc.
>
> I haven't use any non-in-circuit programmable parts in years now; I'm
amazed
> that anyone still does.

I havent designed in any pld's for ages :)

Colin =^.^=


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