9 Apr
2002
9 Apr
'02
10:38 p.m.
Tony Duell wrote:
For experimental and educational projects I much
prefer TTL (including,
of course the CMOS versions of the TTL chips, like 74HCxxx parts). It's
easier to prototype with, easier to test (you can clip the 'scope or
logic analyser wherever you like), and easier to see what's really going
on. It's quicker to make small changes to the circuit as well (on an FPGA
design I did about 5 years ago, a full compile of the main chip took
overnigh (OK, PCs have got faster since then, but FPGAs have also got
larger!)). That meant every small change took a day to test. A soldering
iron and/or wire-wrap tool is a lot faster for changing a few connections
:-) You also aren't tied to a proprietry program running on some
computer/OS that I don't have...
Until I got over 95% of logic filled in my Altera FPGA, most compiles
were under 15 minutes.( BTW -- Since I have 100% of the FPGA used it is
time to stop upgrading the design :)). I live in the middle of (looks
around) snow thus getting stuff mail order is the only way to get parts
often from the USA but some even from Australia.
Please don't attempt to convince me that FPGAs
make more sense for
production. I don't need convincing of that...
TTL is still better for production. (grin).
I wouldn't call those SSI parts.
Ok SSI and MSI parts. Compared to millions of transistors in a cpu, all
TTL parts are small. BTW altera has a fairly nice macro library for
their FPGA's.
Why? The '181 has many more operations, some of
them useful....
I want A+~B,~A+B,A+B,A^B,A|B,A*B alu functions. The 181 can't
give me
that.
Sure... I guess 74x170s are really hard to find now
:-(.. All these
wonderful chips I grew up using are discontinued :-(
More like a 74xx00. The Tiny chips are sure popular today, who would of
thought single gate chips would sell.
--
Ben Franchuk - Dawn * 12/24 bit cpu *
www.jetnet.ab.ca/users/bfranchuk/index.html