18 Dec
2005
18 Dec
'05
8:22 a.m.
On 12/17/2005 at 10:37 PM woodelf wrote:
sites.
I downloaded some motorola application notes from
bitsavers.
Wow they sure had a lot of different types of TTL. I wonder how only
the 74xx became the only TTL used today?
I think the short answer is "second sources"--you had at least 4 big
players, TI, National, Moto and Fairchild all producing 7400-series logic.
Some of the earlier TTL (Moto 400/500-series) had mid-line (pins 4 and10)
power supplies, which turned out to be not as convienient for PCB layout.
And, although it's largely forgotten, 7400 TTL shares a fair number of
pinouts with the older DTL circuits.
By the time LSTTL was out, everyone had pretty much standardized on the
74xx line.
My guess, anyway.
Cheers,
Chuck