pa2384@sdcc13.ucsd.edu (G. Clark) (04/07/90)
Hi all! Can someone tell me if a 74F74 is just a 74H74 in disguise? I've never seen 'F TTL before. Is this Fairchild's high-speed TTL? What does the F stand for 'fast' or fairchild ;-)! Thanks, Gary M Clark pa2384@ucsd.edu
mark@mips.COM (Mark G. Johnson) (04/07/90)
In article <9561@sdcc6.ucsd.edu> pa2384@sdcc13.ucsd.edu (G. Clark) writes: > > Can someone tell me if a 74F74 is just a 74H74 in disguise? >I've never seen 'F TTL before. Is this Fairchild's high-speed TTL? >What does the F stand for 'fast' or fairchild ;-)! "FAST" == Fairchild's Advanced Schottky Technology. It's a completely new circuit family and a new more advanced semiconductor fabrication process. The circuit family uses a different internal arrangement of transistors, diodes, resistors, and capacitors than the other TTL-like families. It isn't 74H or 74S or 74AS or 74ALS. It's 74F. Curious that you should mention 74H. It was the speediest TTL for only a very brief period. 74H used high currents and gold-doped junctions for high speed, but the 74S family quickly appeared and wiped 74H practically off the face of the earth. 74S is faster and lower power than 74H. And now 74F is faster still. Life marches on. A few parts from TI are even faster than 74F, but TI will gladly sell you 74F as well; it's a "standard" you know. Get a FAST databook from Signetics and read the intro chapters on the circuit family. Then post to the net an explanation of the "Miller killer" (not making this up, honest) circuit within the gate that makes 74F so doggone fast. -- -- Mark Johnson MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086 (408) 991-0208 mark@mips.com {or ...!decwrl!mips!mark}
henry@utzoo.uucp (Henry Spencer) (04/08/90)
In article <37746@mips.mips.COM> mark@mips.COM (Mark G. Johnson) writes: >wiped 74H practically off the face of the earth. 74S is faster and >lower power than 74H. And now 74F is faster still. Life marches on. Actually, 74F is a Really Nice family. Not only is it fast as blazes, it tends to eat a lot less power than 74S, and is better-behaved in all kinds of little ways. Not least of its virtues is that since it came from Fairchild, it has truly exemplary datasheets, which pin down both minimum and maximum times and do so over the full temperature and voltage range, unlike most TTL datasheets. I assume this was a general Fairchild characteristic, since the F100K ECL datasheets likewise made 10K datasheets look like toilet paper by comparison. And now they're part of National. Sigh. -- Apollo @ 8yrs: one small step.| Henry Spencer at U of Toronto Zoology Space station @ 8yrs: .| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
logajan@ns.network.com (John Logajan) (04/08/90)
henry@utzoo.uucp (Henry Spencer) writes: >Actually, 74F is a Really Nice family. Not only is it fast as blazes, it >tends to eat a lot less power than 74S, and is better-behaved in all kinds >of little ways. I use 74F parts here at Network almost exclusively for my logic needs. It has the good gate propagations speeds (6ns worst for simple gates and 10ns clock to Q delays on most registers.) You can run into problems at these speeds due to the need to account for speed of light delays in connecting foils between IC's. We don't use a lot of line termination, but I have seen enough cases where it is sometimes advisable (hint, if the line is long and/or the frequency/pulse is high/fast.) You get signal reflection in all unterminated lines, but at high speeds there may not be enough time in your design to let it settle out. And our designs are always pushing the edge. The new kid on the block is 74FCT and 74FC (F.A.C.T.) which are almost as fast as 74F, but are really CMOS based familes (with 74FCT being voltage level compatible with TTL.) Naturally their power requirements are less still than 74F. >Not least of its virtues is that since it came from Fairchild, it has >truly exemplary datasheets, which pin down both minimum and maximum times >and do so over the full temperature and voltage range, unlike most TTL >datasheets. Knowing minimum times becomes essential at high speeds due to the fact that your clock skew between parts, say one register feeding another, may start to exceed your minimum propogation time -- thus you could "short-path". I.E. your data could arrive at the inputs to the next stage before that stage saw it's clock. When the clock does arrive, it will clock thru the new data, rather than the "previous" data. In effect, you will have your data getting through two stages of registers in ONE clock time. Very bad if you aren't expecting it!!! Of course, you can design around this problem with careful matching of clock foil lengths, and other clock distribution techniques, but even then, your clock fanout parts may have part-to-part speed variations that begin to exceed your minimum times. (I hate parts that spec ZERO as minimum times. You know they are lying because they don't want to have to control the minimum time. Fortunately, most such parts are inbetween parts with spec'd minimums. But processors always give me grief. I know that I am actually designing things that violate the theoretical spec/skew problem, but I know that there are no such beasties as ZERO delay parts -- YET.) -- - John Logajan @ Network Systems; 7600 Boone Ave; Brooklyn Park, MN 55428 - logajan@ns.network.com, john@logajan.mn.org, 612-424-4888, Fax 424-2853
peg@psuecl.bitnet (PAUL E. GANTER) (04/08/90)
In article <1990Apr8.000826.16803@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes: > > Not least of its virtues is that since it came from Fairchild, it has > truly exemplary datasheets, which pin down both minimum and maximum times > and do so over the full temperature and voltage range, unlike most TTL > datasheets. I assume this was a general Fairchild characteristic, since > the F100K ECL datasheets likewise made 10K datasheets look like toilet > paper by comparison. Could you post Fairchild's address? I'd like to get a 74F databook (the Amiga uses a good bit of it). Thanks! Paul
henry@utzoo.uucp (Henry Spencer) (04/09/90)
In article <1990Apr8.061809.6501@ns.network.com> logajan@ns.network.com (John Logajan) writes: >... (I hate parts that spec ZERO as minimum >times. You know they are lying because they don't want to have to control >the minimum time... I could live with this in logic (which probably just means that I'm not pushing the logic very hard...) but I really hate it when EPROMs specify zero data hold time after input changes. It makes it quite impossible to do simple interfaces to micros without violating the theoretical rules. At least the RAM manufacturers don't pull this vile trick. -- Apollo @ 8yrs: one small step.| Henry Spencer at U of Toronto Zoology Space station @ 8yrs: .| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
dalyb@godzilla.UUCP (Brian Daly) (04/09/90)
In article <9561@sdcc6.ucsd.edu>, pa2384@sdcc13.ucsd.edu (G. Clark) writes: > Can someone tell me if a 74F74 is just a 74H74 in disguise? > I've never seen 'F TTL before. Is this Fairchild's high-speed TTL? > What does the F stand for 'fast' or fairchild ;-)! > The 74F logic family is the "FAST" logic family. This logic family is not restricted to Fairchild (for example, TI also has an "F" family). The 74F74 is not a 74H74 in disguise. I'd recommend that you obtain an F Logic Databook from TI for further information. -- Brian K. Daly WB7OML @ AG Communication Systems, Phoenix, Arizona UUCP: {...!ames!ncar!noao!asuvax | uunet!zardoz!hrc | att}!gtephx!dalyb Phone: (602) 582-7644 FAX: (602) 582-7111 ~
henry@utzoo.uucp (Henry Spencer) (04/10/90)
In article <103119@psuecl.bitnet> peg@psuecl.bitnet (PAUL E. GANTER) writes: >Could you post Fairchild's address? I'd like to get a 74F databook... Alas! They were bought by National. The good die young... -- Apollo @ 8yrs: one small step.| Henry Spencer at U of Toronto Zoology Space station @ 8yrs: .| uunet!attcan!utzoo!henry henry@zoo.toronto.edu
phil@pepsi.amd.com (Phil Ngai) (04/10/90)
In article <1990Apr8.061809.6501@ns.network.com> logajan@ns.network.com (John Logajan) writes: |We don't use a lot of line termination, but I have |seen enough cases where it is sometimes advisable (hint, if the line is |... |The new kid on the block is 74FCT and 74FC (F.A.C.T.) which are almost as |fast as 74F, but are really CMOS based familes (with 74FCT being voltage |level compatible with TTL.) Naturally their power requirements are less |still than 74F. I haven't used 74FC but I have used 74AC parts and in my experience, the 74AC parts are much worse than any other TTL compatible parts, including the F series, in requiring line termination. Are FC parts better? What is the difference between FC and AC? -- Phil Ngai, phil@amd.com {uunet,decwrl,ucbvax}!amdcad!phil The War on Drugs is the modern day Inquisition.
logajan@ns.network.com (John Logajan) (04/10/90)
henry@utzoo.uucp (Henry Spencer) writes: >In article <103119@psuecl.bitnet> peg@psuecl.bitnet (PAUL E. GANTER) writes: >>Could you post Fairchild's address? I'd like to get a 74F databook... > >Alas! They were bought by National. The good die young... I think Fairchild still exists as "department" of National. They didn' t just buy Fairchild to chuck it in the dustbin. They are clearing out redundant product lines, but they aren't necessarily just dumping the Fairchild versions. -- - John Logajan @ Network Systems; 7600 Boone Ave; Brooklyn Park, MN 55428 - logajan@ns.network.com, john@logajan.mn.org, 612-424-4888, Fax 424-2853
clm@shumv1.ncsu.edu (Christopher Lee McGugan) (04/10/90)
Hey... all you need to do is to check your local phone directory for a listing of National Semiconductor and call them. They stock those sort of books. Also, do you really need the Fairchild databook, the 74F74 is in the TI and the Natioanl Semiconductor databooks. I think that I have the last year issues of the Fairchild series if you need it. -chris
logajan@ns.network.com (John Logajan) (04/11/90)
phil@pepsi.AMD.COM (Phil Ngai) writes: >I haven't used 74FC but I have used 74AC parts and in my experience, >the 74AC parts are much worse than any other TTL compatible parts, >including the F series, in requiring line termination. > >Are FC parts better? What is the difference between FC and AC? The FC parts are different from the AC parts in that there is no such thing as FC parts :-) SORRY, I meant to say AC and ACT parts are the designations for F.A.C.T. (Fairchild Advanced CMOS Technology.) ACT parts have TTL compatible input circuits, whereas AC parts need CMOS levels. Both ACT and AC outputs swing the full CMOS range, which certainly would seem to imply a greater need for termination in high speed use. AC/ACT parts run with supply voltages from 2 to 6 volts, use 1/10th of the power of FAST or ALS, and 1/20th the power of LS (under 1 Mhz.) AC/ACT also has good noise immunity 1.25v/1.25v and can source or sink 24 ma. Maximun propagation delay FAST vs FACT (ACT. AC's are slightly slower.) 74F374 (8 bit F/F) vs 74ACT374 10ns 11.5ns 74F00 (nand) vs 74ACT00 6ns 9.5ns FACT parts sure look good on paper. -- - John Logajan @ Network Systems; 7600 Boone Ave; Brooklyn Park, MN 55428 - logajan@ns.network.com, john@logajan.mn.org, 612-424-4888, Fax 424-2853
ISW@cup.portal.com (Isaac S Wingfield) (04/11/90)
Henry Spencer writes (concerning Fairchild):
>Alas! They were bought by National. The good die young...
?????
How long has Fairchild been in the semiconductor business, compared to
National? Weren't they one of the first companies in the field?
Isaac
isw@cup.portal.com
henry@utzoo.uucp (Henry Spencer) (04/11/90)
In article <28794@cup.portal.com> ISW@cup.portal.com (Isaac S Wingfield) writes: >>Alas! They were bought by National. The good die young... > ????? > >How long has Fairchild been in the semiconductor business, compared to >National? Weren't they one of the first companies in the field? Hey, it's a young field... :-) -- With features like this, | Henry Spencer at U of Toronto Zoology who needs bugs? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
ISW@cup.portal.com (Isaac S Wingfield) (04/12/90)
John Logajan writes: >ACT parts have TTL compatible input circuits, whereas AC parts need CMOS >levels. Both ACT and AC outputs swing the full CMOS range, which certainly >would seem to imply a greater need for termination in high speed use. I believe that edge rate (transition time) is a more significant indicator of the need for termination (and also how much noise radiation is likely) than voltage swing per se. As edge rate goes up, more and more energy shows up at higher frequencies; at higher frequencies, shorter and shorter traces begin to exhibit the transmission line effects that make termination necessary. For equal propagation delays (and therefore equal system speeds), different logic families have different edge rates, and so some will require terminations, and similarly will be much noisier, while others will not. Sorry, but I've been out of hard-nosed design for a while, and can't comment on which of the current families are which... Isaac isw@cup.portal.com