> 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_at_dittman.net
Check out the DEC Enthusiasts Club at http://www.dittman.net/
Received on Sat Oct 06 2001 - 19:14:22 BST