6 Oct
2001
6 Oct
'01
12:14 p.m.
The 1772 and 1770 were designed specifically for use
with the 5-1/4" units,
though that's not necessarily what their use today may be.
I've never seen the 1773 in the flesh, though I've got a data sheet somewhere
(though I've managed to hide it somewhere). The three chips are all similar,
though not identical, in that they have the same data/clock separator circuitr
and write precomp circuit. However, the 1773 lacks some signals that are on the
1770/72, thereby rendering it less "dedicated" to 5-1/4" drives. The
datasheet
did, IIRC, specifically indicate that they're all similar in commands, etc,
though the timing parameters differ somewhat in that the 1770 is slower than the
otherwise identical 1772 in terms of its step rate settings. If I could lay
hands on the 1770/2/3 datasheet, I could tell you which pins differ and in what
sense, but ...
The 1773 is also dedicated to 5.25" drives. Your email jogged my memory, and
indeed the difference between the 1770 and 1773 was a couple of different
signals. I've used the exact same code on both of them. From a programming
point of view they are the same. I don't think there was a version of the
1773 with the faster step rates like in the 1772.
If somebody's got a 1773 and wants a 1770,
I'll happily swap 'em, just so I have
one in house.
If you find a gate array TRS-80 Model 4 then you'd have your 1773.
--
Eric Dittman
dittman(a)dittman.net
Check out the DEC Enthusiasts Club at http://www.dittman.net/