6 Oct
2001
6 Oct
'01
11:22 a.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 ...
If somebody's got a 1773 and wants a 1770, I'll happily swap 'em, just so I
have
one in house.
Dick
----- Original Message -----
From: "Eric Dittman" <dittman(a)dittman.net>
To: <classiccmp(a)classiccmp.org>
Sent: Saturday, October 06, 2001 4:16 PM
Subject: Re: 6502 BASIC or Assembler and Intel 8271/WDC 1770 info req'd
> > So now I'm left with two questions:
> > 1) Has anyone got any source code for the WD1770? 6502 ASM, C,
anything.
The 1770 is pretty much compatible with the other Western Digital FDCs.
The TRS-80 model 4 uses the 1793 (very similar in software), and the
sources of LS-DOS 6.3.1 are on the web somewhere (Tim Mann's page?).
That's Z80 assembly language.
The later (gate array) TRS-80 Model 4 systems used a 1773 FDC, which was
compatible with the 1793. The 1770 and 1773 were compatible, differing
only in the logic states of some of the lines, but it's been so long
since I've used either I can't remember which pins were different.
The 1770/1772/1773 had both the data separator and write precompensation
built-in. They are 28 pin devices (the 1793 is a 40 pin device).
--
Eric Dittman
dittman(a)dittman.net
Check out the DEC Enthusiasts Club at http://www.dittman.net/