14 Dec
2010
14 Dec
'10
11:11 a.m.
On 2010 Dec 14, at 2:41 AM, Christian Corti 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.
We've had this discussion before. TI's earliest RTL/DTL series were
3-digit (e.g. SN53x, SN51x), but I have never seen evidence that the
5400/7400 series began as 540/740. TI docs I have indicate the series
began as 4-digit SN54xx. They were in 14-pin flat-paks, but as you say
with power on the center pins, and very different pinouts from the
later DIPs.
Fairchild claimed to have developed the DIP, most of their early
TTL/DTL stuff had power on the corner pins (there are exceptions, and
some of their other series such as CTL used other pins). It may be that
TI adopted the Fairchild pinouts when TI moved to DIPs.
(The weird thing about the 7490 is power is on neither the corner pins
(7,14) nor the center pins (4,11).
On Mon, 13 Dec 2010, Brent Hilpert wrote:
The 3900, 4500 are definitely DTL. I did obtain a single page
containing pinouts and internal schematic for 3900/4500 ICs with one
calculator that uses them. I just mentioned those series as another
example of TI producing 'oddball' series.
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).