Async FIFO chips?

Tim Watts
Guest

Fri Feb 19, 2010 9:01 pm

Hi,

I saw a rather interesting Elektor article (Feb 2003) for building a cheap
40MHz logic analyser using an AVR and one or more 9 bit FIFOs with storage
for many kilo words.

The chips in question were the IDT720x series or their Cypress version the
CY7C462 and friends.

Had it in mind to build one of these next year (hobby, not production), but
the IDT and CY chips seem to have become seriously discontinued in DIP
format - Digikey are down to the last 18 of one of the IDT chips and most of
the rest are unavailable.

Anyone know of any other async fifo memory chips? I've hunted and those
seemed to be the only ones in that class. Looking for:

4+ bits wide (could manage with 1 bit devices);
40+MHz clock
at least 4k words, 16k better.
DIP package.

I know chips go obselete, but it seems weird for a whole class to disappear
(or at least be only available in SMT format - I prefer to socket my chips
and I'm not up on SMT soldering Sad

).

Many thanks

Tim

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.

Jon Elson
Guest

Sat Feb 20, 2010 12:44 am

Tim Watts wrote:

Quote:

Hi,

I saw a rather interesting Elektor article (Feb 2003) for building a cheap
40MHz logic analyser using an AVR and one or more 9 bit FIFOs with storage
for many kilo words.

The chips in question were the IDT720x series or their Cypress version the
CY7C462 and friends.

Had it in mind to build one of these next year (hobby, not production), but
the IDT and CY chips seem to have become seriously discontinued in DIP
format - Digikey are down to the last 18 of one of the IDT chips and most of
the rest are unavailable.

Anyone know of any other async fifo memory chips? I've hunted and those
seemed to be the only ones in that class. Looking for:

4+ bits wide (could manage with 1 bit devices);
40+MHz clock
at least 4k words, 16k better.
DIP package.

I know chips go obselete, but it seems weird for a whole class to disappear
(or at least be only available in SMT format - I prefer to socket my chips
and I'm not up on SMT soldering Sad

).
If they've got them in SMT, you can get adaptor boards to go from most

common SMT footprints to DIP. Soldering low-density SMT's isn't any big
deal, a small soldering tip and a little magnifier hood is all you need.

Jon

Jon Elson
Guest

Sat Feb 20, 2010 12:50 am

Tim Watts wrote:

Quote:

I know chips go obselete, but it seems weird for a whole class to disappear
Oh, and don't get me started on obsolete, hard to get, etc. stuff!

YIKES! I design a prototype, and while buying the parts, notice
Digi-Key has 40,000 pieces on hand. Ah, good supply, no problem.
Then, I revise the board and order a bunch and go back to Digi-Key to
get 100 pieces of the parts, suddenly they have no stock, its a
discontinued part, AIEEEEE!!! And, I have 100 blank boards coming and
can't get the chips anymore. Don't ask me how many times this has
happened, it is driving me nuts! Or, I find that Digi-Key or other
Distributor has placed a 2000-piece minimum order on the part, but they
have 137 pieces showing as "in stock". How the HELL will they ever get
those 137 pcs. off their shelves if they will only sell 2000-piece lots?
Some of these are expensive parts, so you have to buy $25,000 lots or
none. It is definitely making Digi-Key especially, pretty non-friendly
to small manufacturers.

Jon

Tim Watts
Guest

Sat Feb 20, 2010 11:32 am

Jon Elson <jmelson_at_wustl.edu>
wibbled on Friday 19 February 2010 23:44

Quote:

If they've got them in SMT, you can get adaptor boards to go from most
common SMT footprints to DIP. Soldering low-density SMT's isn't any big
deal, a small soldering tip and a little magnifier hood is all you need.

I suppose so, Jon.

I was browsing Farnell last night. Despite the fact you can now get 74HC4017
counters running at 83MHz for less pence than they cost when I was a kid in
1980, they *still* sell CD4017s. 741, 555 no problem.

I can understand a specific chip buggering off, but not a whole class of DIP
based large memory fast fifos, which seem more general purpose than
specialist... I found http://www.xs4all.nl/~ganswijk/chipdir/ and so far
haven't found anything in the fifo section that's still in stock (haven't
got to the end mind).

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.