Re: 74LS90, 74LS92 and other TTL are OBSOLETE???

In article <1142276909.257399.27560@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
pdmtr <pdmtr@xxxxxxxxx> wrote:

Yes of course it can be replaced by a uCU... or a CPLD, FPGA, ASICs,
etc!
The question is, WHY to replace a simple <10cents Ic with a >1$ (+ cost
to make the code) one to do the job??? if you just need to do only the
ting the TTL logic does?
Do they going nut (IC makers) or ... ?

No, they're not nuts.

It's simply a matter of economics. Decades ago, most digital
electronics were build around this sort of part - the manufacturing
volumes were extremely high and they were churned out like jellybeans.

These days, most consumer electronics devices no longer use such
parts... because it's possible to make TVs, VCRs, computers, etc. with
more modern parts that are smaller, faster, use less power, and are
easier to handle on modern high-speed manufacturing lines.

In short, the actual demand for small-scale-integration TTL parts in
large packages has died. The total world demand for such parts is
probably a small fraction of a percentage of what it was, decades ago.

At this point, there's just no longer an incentive for manufacturers
to keep making and stocking them. It's more trouble and money than
it's worth to them. I'd guess that the cost of maintaining the older
wafer-fabrication lines used for these old designs becomes prohibitive.

For modern designs, nobody replaces a single $.10 IC with a $1 PIC or
CPLD unless they absolutely have to.

Instead, they design a single board which uses $5 worth of micros and
ASICs and FPGAs, but which does the same job (or a better job) than a
rack of large boards which used hundreds or thousands of $.10 ICs.

The large-volume parts buyers no longer want 74LSxxx DIP parts.

--
Dave Platt <dplatt@xxxxxxxxxxxx> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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