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