5 Apr
2013
5 Apr
'13
1:30 p.m.
Is there anybody who knows what is this old chip? And where to try to find
it?
I've seen 733Wxxx house codes on Xerox chips before, but hav never seen
the equivalents list.
If it help what I know is that it used to do somenting like shift data
register or Serial Shift Registers.
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
Wait a second. You said jsut now it has 14 pins, and you give a signal
for pin 15. Does it have a top cap or something :-)
More seriousyl, if it's actually a 16 pin IC, I would guess it's a
programmed 74x188 (open collector) or more likely 74x288 (3-state output)
PROM. That's a 32*8 bit device that goes udner a variety of other
numbers too, like 18S030. Fiffernt manufacturers had differnt programming
algorithms, but the all work the same way in-circuit (in read mode).
The pinout is :
1 : D0
2 : D1
3 : D2
4 : D3
5 : D4
6 : D5
7 : D6
8 : Gnd
9 : D7
10 : A0
11 : A1
12 : A2
13 : A3
14 : A4
15 : CE/
16 : Vcc
This could match your device, A4 is tied high (so only useing the second
half of the ROM) and only the first 4 data lines are used.
Of course the problem for you, I guess, is that a blank chip of the right
type is of little use to you. You need to konw the contents (looks to be
16 4-bit words in your case). You could copy it from a working device fro
the same type of machine, but other than that uou have some designing to
do...
-tony