Why no current-process shift registers?

A

Alex Rast

Guest
I am constantly running into a need for a shift register in my designs to
convert serial to parallel data (or vice versa). Yet as far as I've found,
the most "modern" one available is the Fairchild 74AC299. It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?

Why do none seem to be made? It seems to me almost self-evident that
somehow there must not be the demand, but I'm baffled as to how that could
be so? Aren't people needing high-speed serial/parallel or parallel/serial
conversion any more? If not, why not? If it's still a function that they
need, what are they using? Please don't tell me that people are using an
SRAM combined with a counter. If so, what an inefficient design, with more
needed components, more complex interfacing, wasted SRAM bits, etc!
--
Alex Rast
ad.rast.7@nwnotlink.NOSPAM.com
(remove d., .7, not, and .NOSPAM to reply)
 
In article <93C3B61ECadrastnwnotlinkcom@216.168.3.44>,
ad.rast.7@nwnotlink.NOSPAM.com (Alex Rast) writes:
<...>
|> Why do none seem to be made? It seems to me almost self-evident that
|> somehow there must not be the demand, but I'm baffled as to how that could
|> be so? Aren't people needing high-speed serial/parallel or parallel/serial
|> conversion any more? If not, why not? If it's still a function that they
|> need, what are they using? Please don't tell me that people are using an

When you have FPGAs or CPLDs, you never want to play with those function
limited TTL-stuff again ;-)

--
Georg Acher, acher@in.tum.de
http://wwwbode.in.tum.de/~acher
"Oh no, not again !" The bowl of petunias
 
Alex Rast wrote:
I am constantly running into a need for a shift register in my designs to
convert serial to parallel data (or vice versa). Yet as far as I've found,
the most "modern" one available is the Fairchild 74AC299. It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?

Why do none seem to be made? It seems to me almost self-evident that
somehow there must not be the demand, but I'm baffled as to how that could
be so? Aren't people needing high-speed serial/parallel or parallel/serial
conversion any more? If not, why not? If it's still a function that they
need, what are they using? Please don't tell me that people are using an
SRAM combined with a counter. If so, what an inefficient design, with more
needed components, more complex interfacing, wasted SRAM bits, etc!
--
Alex Rast
ad.rast.7@nwnotlink.NOSPAM.com
(remove d., .7, not, and .NOSPAM to reply)
Click to expand...
Use a PIC instead.

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com fax 847-574-1462

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
On Sat, 26 Jul 2003 00:53:03 -0000, the renowned
ad.rast.7@nwnotlink.NOSPAM.com (Alex Rast) wrote:

I am constantly running into a need for a shift register in my designs to
convert serial to parallel data (or vice versa). Yet as far as I've found,
the most "modern" one available is the Fairchild 74AC299. It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?

Why do none seem to be made? It seems to me almost self-evident that
somehow there must not be the demand, but I'm baffled as to how that could
be so? Aren't people needing high-speed serial/parallel or parallel/serial
conversion any more? If not, why not? If it's still a function that they
need, what are they using? Please don't tell me that people are using an
SRAM combined with a counter. If so, what an inefficient design, with more
needed components, more complex interfacing, wasted SRAM bits, etc!
Click to expand...
Unless it's a really simple function, (including wide latches and
transceivers) or HC can do the trick, a PLD/CPLD/FPGA is the way to
go!

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
On Sat, 26 Jul 2003 00:53:03 -0000, ad.rast.7@nwnotlink.NOSPAM.com
(Alex Rast) wrote:

I am constantly running into a need for a shift register in my designs to
convert serial to parallel data (or vice versa). Yet as far as I've found,
the most "modern" one available is the Fairchild 74AC299. It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?

Why do none seem to be made? It seems to me almost self-evident that
somehow there must not be the demand, but I'm baffled as to how that could
be so? Aren't people needing high-speed serial/parallel or parallel/serial
conversion any more? If not, why not? If it's still a function that they
need, what are they using? Please don't tell me that people are using an
SRAM combined with a counter. If so, what an inefficient design, with more
needed components, more complex interfacing, wasted SRAM bits, etc!
Click to expand...
"Functional" logic chips are disappearing, being replaced by PLDs and
FPGAs. I recently did an FPGA design that had a 160-bit shift register
inside... brute force deserialization. Most new standard-logic gadgets
are datapath parts or glue logic, and a lot of glue is single-gate
TinyLogic sort of stuff.

John
 
I am constantly running into a need for a shift register in my designs to
convert serial to parallel data (or vice versa). Yet as far as I've found,
the most "modern" one available is the Fairchild 74AC299. It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?

Why do none seem to be made? It seems to me almost self-evident that
somehow there must not be the demand, but I'm baffled as to how that could
be so? Aren't people needing high-speed serial/parallel or parallel/serial
conversion any more? If not, why not? If it's still a function that they
need, what are they using? Please don't tell me that people are using an
SRAM combined with a counter. If so, what an inefficient design, with more
needed components, more complex interfacing, wasted SRAM bits, etc!
Click to expand...
Have you discovered the principle of cascading?
 
"Alex Rast" <ad.rast.7@nwnotlink.NOSPAM.com> wrote in message
news:93C3B61ECadrastnwnotlinkcom@216.168.3.44...

It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?
Click to expand...
There are current-technology shift-registers, they're just given fancier
names these days.
Look at ti's web site, I think under "gigabit" or "fiber" transcievers, they
have some
32-bit 2-GHz shift registers.
 
Jim Backus schrieb:

Can you recommend a FPGA / CPLD family that offers low cost
development tools and easy to understand documentation.

I'd like to investigate these but can't afford to stump up 1,000s of
GBP for the kit.
Click to expand...
Look at XC95(XL) family from Xilinx.
They have a complete development software (VHDL etc.) for free
download after registration.
The JTAG programmer cable can be built by yourself, the circuit is
published (connects to the LPT port). Or buy one, it's not so
expensive.

I think the other big players (like Lattice and Actel) also have
comparable tools, however Xilinx is the only one who supports
VHDL in the free software already, AFAIK.


--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
http://www.autometer.de

==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)
 
On Sat, 26 Jul 2003 01:21:09, acher@in.tum.de (Georg Acher) rolled up
his sleeves and typed:

When you have FPGAs or CPLDs, you never want to play with those function
limited TTL-stuff again ;-)
Click to expand...
Can you recommend a FPGA / CPLD family that offers low cost
development tools and easy to understand documentation.

I'd like to investigate these but can't afford to stump up 1,000s of
GBP for the kit.

--
Jim Backus OS/2 user
bona fide replies to jimb-thecirclethingy-jita-dp-demon-dp-co-dp-uk
or remove "NOT" from address
remove dashes and make the obvious substitutions for valid email
address
 
Check out the SERDES line of devices. They implement 10/8b encoding &
decoding, error detection, and large width data transfer at speeds of 100Mhz
or more. This is the direction the industry is going.

Hope this helps.
Dana Raymond


"Alex Rast" <ad.rast.7@nwnotlink.NOSPAM.com> wrote in message
news:93C3B61ECadrastnwnotlinkcom@216.168.3.44...
I am constantly running into a need for a shift register in my designs to
convert serial to parallel data (or vice versa). Yet as far as I've found,
the most "modern" one available is the Fairchild 74AC299. It would be very
nice, indeed, almost mandatory, to find parts with more modern processes
(2.5/1.8/1.5V logic), and wider word sizes (32-bit?). Are there any parts
out there you can recommend?

Why do none seem to be made? It seems to me almost self-evident that
somehow there must not be the demand, but I'm baffled as to how that could
be so? Aren't people needing high-speed serial/parallel or parallel/serial
conversion any more? If not, why not? If it's still a function that they
need, what are they using? Please don't tell me that people are using an
SRAM combined with a counter. If so, what an inefficient design, with more
needed components, more complex interfacing, wasted SRAM bits, etc!
--
Alex Rast
ad.rast.7@nwnotlink.NOSPAM.com
(remove d., .7, not, and .NOSPAM to reply)
Click to expand...
 
at Sat, 26 Jul 2003 12:03:24 GMT in <3F226DFC.5070300@nospam.com>,
nospam@nospam.com (Fred Bloggs) wrote :

I am constantly running into a need for a shift register in my designs
to convert serial to parallel data (or vice versa)... It
would be very nice,... to find parts with ... wider word sizes
(32-bit?).

Have you discovered the principle of cascading?

Although this is beating a bit of a dead horse, why go through all the
Click to expand...
trouble of higher component count? Sure, you can cascade, but this means
more parts, (bypass caps as well as IC's) trickier PCB routing, higher
board area, and possibly even delay effects (from the fact that the cascade
lines go off-chip). It seems to me as though once again you're
incorporating higher cost and complexity for no benefit.

What I'm seeing and surmising, based on the responses to date, is that most
people end up with designs containing quite a lot of glue logic, so that a
PLD is an attractive option. I find that my designs typically have only a
very small amount, perhaps one or 2 potential components, of glue logic. I
gather from the replies so far that this is a relatively rare situation.


--
Alex Rast
ad.rast.7@nwnotlink.NOSPAM.com
(remove d., .7, not, and .NOSPAM to reply)
 
ad.rast.7@nwnotlink.NOSPAM.com (Alex Rast) wrote:

at Sat, 26 Jul 2003 01:21:09 GMT in <bfsl25$40r$1@wsc10.lrz-muenchen.de>,
acher@in.tum.de (Georg Acher) wrote :

In article <93C3B61ECadrastnwnotlinkcom@216.168.3.44>,
ad.rast.7@nwnotlink.NOSPAM.com (Alex Rast) writes:
...
|> Why do none seem to be made? ... Aren't people needing high-speed
|> serial/parallel or
|> parallel/serial conversion any more? If not, why not?

When you have FPGAs or CPLDs, you never want to play with those function
limited TTL-stuff again ;-)


Sometimes that's a good option. But other times it makes little sense. Our
design in fact has 2 large FPGA's on board. One might ask, why not use
them? In this case, the answer is that they sit on the "other side" of a
plug-in connector carrying a module. On the module I have no real need for
an FPGA/CPLD other than for this one little function, and it would be silly
to put one on there for that purpose alone, especially when you've got 2
already.

In addition there are more general reasons why the PLD approach isn't
necessarily a panacaea. First, if your logic function is small and self-
contained, you're wasting an awful lot of chip resources, if that one
function is all you need. Second, the chips require more support : full
support chips in the case of an FPGA (at least a serial EEPROM), software
Click to expand...
Did you look into I2C chips with a parallel port?

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl
 
Can you recommend a FPGA / CPLD family that offers low cost
development tools and easy to understand documentation.
Click to expand...
Try <http://www.trenz-electronic.de/prod/proden7.htm>, the software is
"free" and the hardware is cheap.
 
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