5 Feb
2010
5 Feb
'10
10:41 a.m.
On 4 Feb 2010 at 19:15, Tony Duell wrote:
When did the 6820 come out?
Even so, the knoweldge that TTL inputs float high, and can more easily be
pulled high than low was very well known at the time. Whoever designed
that chip was not thinkibng aobut how it was going to be used IMHO. I am
not talking aobut somebody finding an application later on for which the
original design wasn't perfect, but actually I can't think of a single
applicaiton where the behaviour of the 8255 is desireable. I can think of
some where it doens't matter, but none where you'd avtually want a chip
that behaves that way.
That's the one. A more stupid design decision
is hard to imagine!
Okay, in Intel's defense, are there any earlier peripheral chips for
the 8-bit bus (I don't count the 8212 and the 8205)?
...and here we are, more than 35 years down the road and you can
still buy the things new. Say what you want about it--it's probably
one of the most durable peripheral chips out there.
And I am still wondering why...
-tony