[sdiy] Another new hard to find part....

[Ingo Debus]

Am Montag, 05.07.04 um 21:09 Uhr schrieb jbv:

> remark 1 : when I compare the time I used to spend 25 years ago 
> designing +
> debugging modules & drilling PCBs full of TTL logic with the ease to 
> design
> the
> same stuff around a uC or a basic stamp, I realize that I don't care 
> much if
> big
> companies decide to drop TTL logic in dip package...
>

IMHO there are three types of digital circuits:
(1) Simple. These are so simple that replacing them with a micro hasn't 
any benefit. So I think very basic TTL ICs like 74xx00 or 74xx74 won't 
be obsolete too soon.
(2) Complex but slow. These are the circuits where 25 years ago for 
instance a 4 bit adder was used, Today a micro is just cheaper, needs 
less real estate on the PCB, less traces (thus more reliable) and is 
much more flexible.
(3) Complex and fast. Here sometimes still things like an adder IC are 
required. But there are also PLDs.

Logic ICs have been obsoleted all the time. Well perhaps not really 
obsoleted, but they didn't make the transition to newer logic families 
(from standard TTL to LS or HC).

If you look at a 10 years old digital design (say a HD drive) the 
percentage of obsoleted parts is probably higher than that of a 30 
years old one (say the keyboard/sequencer circuit of the EMS synthi).

Ingo