5 Apr
2013
5 Apr
'13
9:07 a.m.
------ Original Message ------
From: "Enrico Lazzerini" <enrico.lazzerini at email.it>
To: cctech at classiccmp.org
Sent: 04/04/2013 18:15:52
Subject: Chip 733w01522 on xerox 820-II FDC controller. what is it?
Is there anybody who knows what is this old chip? And
where to try to
find
it?
I believe that its a 74S288 which is 256 bit PROM (32x8) bit prom. So
even if you find one you need to know its contents. Look for an
application note for the 1297.
If it help what I know is that it used to do somenting like shift data
register or Serial Shift Registers.
Often used for state decoding. From searching the web I can see that
there is an FE2100 which is designed to replace the discrete logic on a
FDC board and it mentions the 74S288..
It has a TTL level signal on its pins, it has 14 pins.
You can see it
named
U1 in the centre of this schematic:
<https://www.dropbox.com/s/zqhgar4g7ib5j4z/Xerox820_FDC_Schematic.pdf>
https://www.dropbox.com/s/zqhgar4g7ib5j4z/Xerox820_FDC_Schematic.pdf
Some pins are labelled on a schematics with:
1=D1, 2=D2, 3=D3, 4=D4,
10=A1, 11=A2, 12=A3, 13=A4, 14=A4,
15=ChipEnable (left to GND),
7=GND,
14=+5Vcc
these match the chip outline in my Texas TTL manual (there are 4 more
data outs which are unused in this application)
Thanks
Enrico
Sorry not 100% of needed info
Dave
G4UGM
5 Apr
5 Apr
11:48 p.m.
The problem pretty much solved yesterday (Thursday) on Erik's VCF. My
guess is that it simply takes that long for some messages to post.
Part in question is the 74S288 bipolar PROM and used in the
write-precomp portion of the 820 FDC board. Fortunately, the OP managed
to find the reference design for the WD179x.
I posted on the VCF the web site for a guy who will program 288s for a
very reasonable charge.
--Chuck
6 Apr
6 Apr
9:20 p.m.
The problem pretty much solved yesterday (Thursday) on Erik's VCF. My
guess is that it simply takes that long for some messages to post.
Is there some kind of automatic link between this mailing ist and the
forum? I wasn't aware of one.
I am not on the forum (AFAIK), if you (and others) expect that all of
us are both on the forum and this list, I have to ask what the point is
of having both. And if I am not jus the only person to be on the mailing
list and not the forum, I think it's hardly suprising that there will be
replies on one that are very similar to replies on the other.
Part in question is the 74S288 bipolar PROM and used in the
Do you know this for a fact, or is it just based o nthe pinout?
write-precomp portion of the 820 FDC board.
Fortunately, the OP managed
to find the reference design for the WD179x.
Right...
Incidentalyl, one machine, I think it was the Rainbow, had a little
state machine using a bipolar PROM and a bit of TTL on the FDC board.
This was not anythign to do with write precompensation. Instead, it
encoded a spare ynchronous serial channel into MFM. This was then sed to
verify the operation of the FDC chip during the POST. NEver seen anyone
else go to those lengths,
-tony
10:59 p.m.
On 04/06/2013 01:20 PM, Tony Duell wrote:
I am not on the forum (AFAIK), if you (and others)
expect that all of
us are both on the forum and this list, I have to ask what the point is
of having both. And if I am not jus the only person to be on the mailing
list and not the forum, I think it's hardly suprising that there will be
replies on one that are very similar to replies on the other.
That happens quite a bit, Tony. Erik's VCF tends to be oriented more
toward personal microcomputers (IBM-style PCs, Apple, Commodore, etc.)
although some more unusual stuff does show up, such as the guy
reconstructing a Honeywell H200 system.
Incidentalyl, one machine, I think it was the
Rainbow, had a little
state machine using a bipolar PROM and a bit of TTL on the FDC board.
This was not anythign to do with write precompensation. Instead, it
encoded a spare ynchronous serial channel into MFM. This was then sed to
verify the operation of the FDC chip during the POST. NEver seen anyone
else go to those lengths,
I misspoke in my earlier post (I had something else on my mind). The
subject PROM is part of a data separator circuit. It's been suggested
by one poster that it might be simpler to replace the 2-chip separator
with a WD9216. But that wouldn't be any fun...
--Chuck
4302
days inactive
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