10 Feb
2003
10 Feb
'03
5:09 a.m.
Sellam wrote:
I am looking at a chip that is causing me confusing
with regards to its
actual date code.
The chip is labeled thusly:
(logo) /718
DM74157N
9322
(logo) looks something like this: /\/
/\/
...which probably makes it National Semiconductor.
Yes. The "DM" prefix is also indicative of that. Most other vendors
of 7400 series parts copied the "SN" prefix from TI.
My first instinct is to guess that its date code is
9322. However, it
does not fit within the context of the rest of the board, which is 1976.
The DM74157N was also known as a DM9322, so the part is dual-marked.
They are definitely not original, as the board calls
for a 74257 but the
74157 has been put in its place with the addition of a capacitor across
+5 and ground.
The capacitor is just for additional decoupling, and doesn't change
the function of the chip. The particular board you're looking at (I
can guess what it is) was spec'd for either a 74157 or 74257.
Eric