14 Dec
2010
14 Dec
'10
2:41 a.m.
On Mon, 13 Dec 2010, Brent Hilpert wrote:
Historically, the first SN TTL-ICs had their supply pins in the middle
because they used flat-packs (one would call them SMD today) and not DIPs
which were used later. The SN54xx series was an evolution from the
three-digit series (SN54x), i.e. an SN5400 was like an SN540 but in a
bigger package (something like four instead of three NANDs), and so on.
Christian
Regarding the SN1400 series though, the 74H and 74L
variants are present in
the 1969 TI TTL databook, a little before or around the same time as the
noted SN1400 units. There were lots of other TTL series being produced by
other manufacturers, but the SN1400 one seems odd coming from TI, who had
established the 7400 series years earlier, and the application in a
calculator would or could be adequately covered by the standard series.
Yeah, and I think that it doesn't make sense to have several manufacturers
produce (i.e. TI, Motorola, PH (whatever they are, at least neither
Philips nor Siemens)) a specialized series derived from the 54xx/74xx just
for some calculators. Maybe they used rejects from production and labelled
them differently, or maybe they used hand-picked examples.
Just to see if anything recent was out there, I went
looking on the web for
other references to the SN3900 series and found three sites: one in another
The Canon Canola 1210 for example uses the SN3900 and SN4500 series, IIRC.
And they don't look like TTL at all. I think that I have some pictures
from that machine.
them at 7 and
14 or 8 and 16 for TTL which did simplify layout, but there
are lots of exceptions
even inside the TTL product space. And sometimes there were good reasons
for the
exceptions, other times I think it was just internal squabbling :-)
The 7490 was one that always bugged me, very common and one of the first 2 or
3 IC types I ever used (pins 5/Vcc and 10/GND).