Re: [time-nuts] Performance of 74LVC series ICs
Thanks for all of the replies, very useful. Also for the recommendations on the 74LVC1G74 and 1G80. I don't know why I didn't check for a 7474 in this technology, of course they would have that available. But it looks like the 1G80 will do just exactly what I need in a smaller package, so I think I'll go with that. Dan On Tue, Jun 9, 2015 at 8:52 AM, Dan Kemppainen d...@irtelemetrics.com wrote: Hi Dan, 74LVC1G80. See: http://www.ti.com/lit/ds/symlink/sn74lvc1g80.pdf Might be worth looking at. Dan On 6/9/2015 4:24 AM, time-nuts-requ...@febo.com wrote: Let's say I have a 20MHz TCXO. I want to square up the output signal and divide by two. Easy, just a buffer or inverter and a flip flop. But looking at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not output. So now I need a second inverter to make it toggle. The 74LVC2G14 includes two schmitt inverters in the package, but will isolation inside the device be good enough to use it for two separate functions at 20 and 10 MHz? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
One thing that is hidden in AC and later CMOS is very tightly controlled edge-rate to combat ground bounce. The original AC components were so fast, the ground bounce could be measured in volts and they had to be quickly redesigned. For the D-FF function, you might consider using one section of the dual 74LVC74. With the inputs of the unused section connected to ground or Vdd, it will draw no power. David N1HAC On 6/8/15 8:30 PM, Dan Watson wrote: I have something of a follow up question. How good is the isolation inside these devices (74LVC, SOT-23 package) between gates? Let's say I have a 20MHz TCXO. I want to square up the output signal and divide by two. Easy, just a buffer or inverter and a flip flop. But looking at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not output. So now I need a second inverter to make it toggle. The 74LVC2G14 includes two schmitt inverters in the package, but will isolation inside the device be good enough to use it for two separate functions at 20 and 10 MHz? Just from a layout perspective using three devices instead of two would be easier. However the thing will be battery powered, so I'd like to save the power if possible. Thanks Dan On Mon, Jun 1, 2015 at 6:13 PM, Andy ai.egrps...@gmail.com wrote: The gates on that page http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html use bipolar transistors. The 74LVC parts are CMOS. There are various effects caused by that difference. And those examples have vastly inferior control over input switching levels, compared to just about any well made digital IC from the last half century. (Funny to think that it has been half of a century!) 2N type transistors might have switching delays upwards of 100 ns (depending on load), whereas the LVC parts switch in the 1-5 ns range. On the other hand: A well designed discrete circuit can beat a general purpose integrated circuit in almost all performance measures. Some performance metrics would be hard to beat with even a well designed discrete circuit. On-die capacitance and inductance tends to be much smaller than any discrete circuit can achieve. Andy ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
watsondani...@gmail.com said: Let's say I have a 20MHz TCXO. I want to square up the output signal and divide by two. Easy, just a buffer or inverter and a flip flop. But looking at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not output. So now I need a second inverter to make it toggle. The 74LVC2G14 includes two schmitt inverters in the package, but will isolation inside the device be good enough to use it for two separate functions at 20 and 10 MHz? The simple answer is to use the 74LVC1G74 which has the inverted output. The complicated answer is more complicated. What are you using the inverter for? Clock or data? If both halves are used for data and there is plenty of setup/hold time, then the timing through the chip doesn't matter. If you are using it for a clock, then things get interesting. Is there a fixed phase between the 2 signals? If they never change at the same time, it probably doesn't matter. (How close counts as same might get interesting.) If they do, how nutty are you feeling? If it mattered, I'd probably do something else. The simplest something-else is to use 2 packages. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
Hi Dan, 74LVC1G80. See: http://www.ti.com/lit/ds/symlink/sn74lvc1g80.pdf Might be worth looking at. Dan On 6/9/2015 4:24 AM, time-nuts-requ...@febo.com wrote: Let's say I have a 20MHz TCXO. I want to square up the output signal and divide by two. Easy, just a buffer or inverter and a flip flop. But looking at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not output. So now I need a second inverter to make it toggle. The 74LVC2G14 includes two schmitt inverters in the package, but will isolation inside the device be good enough to use it for two separate functions at 20 and 10 MHz? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
Hi The isolation in the package is likely better than the (practical) layout you will do to mate up with them. In fact, the single gate stuff probably does a better job of isolation than the multi gate stuff, simply because you can spread it out on the board. In the case of dividing by two, there are single gate flip-flops that are Q bar output rather than Q. That eliminates the second single gate package in this design. Yes, there are far to many different numbering systems. Finding this or that can be a massive pain. == If power is an issue, the real trick is to find a family that is happy running on a low(er) supply voltage. Some of this stuff will toggle at 20 MHz with very low supply. Often the inputs are “high voltage tolerant” even with those low supplies. Bob On Jun 8, 2015, at 8:30 PM, Dan Watson watsondani...@gmail.com wrote: I have something of a follow up question. How good is the isolation inside these devices (74LVC, SOT-23 package) between gates? Let's say I have a 20MHz TCXO. I want to square up the output signal and divide by two. Easy, just a buffer or inverter and a flip flop. But looking at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not output. So now I need a second inverter to make it toggle. The 74LVC2G14 includes two schmitt inverters in the package, but will isolation inside the device be good enough to use it for two separate functions at 20 and 10 MHz? Just from a layout perspective using three devices instead of two would be easier. However the thing will be battery powered, so I'd like to save the power if possible. Thanks Dan On Mon, Jun 1, 2015 at 6:13 PM, Andy ai.egrps...@gmail.com wrote: The gates on that page http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html use bipolar transistors. The 74LVC parts are CMOS. There are various effects caused by that difference. And those examples have vastly inferior control over input switching levels, compared to just about any well made digital IC from the last half century. (Funny to think that it has been half of a century!) 2N type transistors might have switching delays upwards of 100 ns (depending on load), whereas the LVC parts switch in the 1-5 ns range. On the other hand: A well designed discrete circuit can beat a general purpose integrated circuit in almost all performance measures. Some performance metrics would be hard to beat with even a well designed discrete circuit. On-die capacitance and inductance tends to be much smaller than any discrete circuit can achieve. Andy ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
Hi The question is always “good isolation compared to what?”. If you are expecting 180 db of isolation on a SOT-23 package at 10’s of MHz, it’s not going to happen. It’s also not going to happen with a practical pc board layout even without the SOT-23 involved. If something around 120 db is “good isolation”, then yes you can do that with a pair of the SC-70 parts and a good layout. In this case the test was at 10 MHz. Bob On Jun 9, 2015, at 12:26 AM, Andy ai.egrps...@gmail.com wrote: I have something of a follow up question. How good is the isolation inside these devices (74LVC, SOT-23 package) between gates? Maybe it's just me ... but I wouldn't trust the isolation to be good. Apart from on-die coupling, they share the same power/ground leads, however short they are. So just getting power and ground from the board onto the die, they would be corrupted by what happens in the other gate and its load (L*di/dt). Andy ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
I have something of a follow up question. How good is the isolation inside these devices (74LVC, SOT-23 package) between gates? Let's say I have a 20MHz TCXO. I want to square up the output signal and divide by two. Easy, just a buffer or inverter and a flip flop. But looking at the pinout of the 74LVC1G175 (D flip flop) it doesn't have a Q not output. So now I need a second inverter to make it toggle. The 74LVC2G14 includes two schmitt inverters in the package, but will isolation inside the device be good enough to use it for two separate functions at 20 and 10 MHz? Just from a layout perspective using three devices instead of two would be easier. However the thing will be battery powered, so I'd like to save the power if possible. Thanks Dan On Mon, Jun 1, 2015 at 6:13 PM, Andy ai.egrps...@gmail.com wrote: The gates on that page http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html use bipolar transistors. The 74LVC parts are CMOS. There are various effects caused by that difference. And those examples have vastly inferior control over input switching levels, compared to just about any well made digital IC from the last half century. (Funny to think that it has been half of a century!) 2N type transistors might have switching delays upwards of 100 ns (depending on load), whereas the LVC parts switch in the 1-5 ns range. On the other hand: A well designed discrete circuit can beat a general purpose integrated circuit in almost all performance measures. Some performance metrics would be hard to beat with even a well designed discrete circuit. On-die capacitance and inductance tends to be much smaller than any discrete circuit can achieve. Andy ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
Thanks for the replies! Very informative. Dan Sent from my iPhone On May 31, 2015, at 6:23 PM, Attila Kinali att...@kinali.ch wrote: On Sun, 31 May 2015 14:06:26 -0400 Dan Watson watsondani...@gmail.com wrote: Has anyone used or experimented with the 74LVC series of ICs? I have found them quite useful in projects. Supply voltage of 2-5V, and two inverters or a single gate or flip flip in a SOT package. They make for much cleaner layouts than large DIPs. Yes, quite a few of those. After CPLDs and FPGAs replaced all of the more complex 74xxx's, people realized that most projects do not need 4 NAND gates at one spot, but rather single ones here and there (a schmitt-trigger for signal conditioning, an AND gate to couple two enable lines,...). I'm wondering if they are acceptable replacements for 74HC, AC, etc in timing circuits. I have never used any of the LVC in a timing circuit, but i would guess they are not worse than the AC. Also they have the advantage of having single gates per package, which helps minimizing cross coupling between different signal paths. BTW: [1] may contain some interesting data for you. Especially as it compares different manufacturers too. Looking at [2], the ALVC family would probably be also worth a look. Attila Kinali [1] Low Voltage Logic Designers Guide, Ti, 1996 http://www.ti.com/lit/ml/scba010/scba010.pdf [2] Logic Guide, Ti, 2014 http://www.ti.com/lit/sg/sdyu001aa/sdyu001aa.pdf -- _av500_ phd is easy _av500_ getting dsl is hard ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
I am curious, how the integrated gates could be compared for those created on discrete elements ? Let say simple gates like this: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html Regards, Vlad On 2015-05-31 18:23, Attila Kinali wrote: On Sun, 31 May 2015 14:06:26 -0400 Dan Watson watsondani...@gmail.com wrote: Has anyone used or experimented with the 74LVC series of ICs? I have found them quite useful in projects. Supply voltage of 2-5V, and two inverters or a single gate or flip flip in a SOT package. They make for much cleaner layouts than large DIPs. Yes, quite a few of those. After CPLDs and FPGAs replaced all of the more complex 74xxx's, people realized that most projects do not need 4 NAND gates at one spot, but rather single ones here and there (a schmitt-trigger for signal conditioning, an AND gate to couple two enable lines,...). I'm wondering if they are acceptable replacements for 74HC, AC, etc in timing circuits. I have never used any of the LVC in a timing circuit, but i would guess they are not worse than the AC. Also they have the advantage of having single gates per package, which helps minimizing cross coupling between different signal paths. BTW: [1] may contain some interesting data for you. Especially as it compares different manufacturers too. Looking at [2], the ALVC family would probably be also worth a look. Attila Kinali [1] Low Voltage Logic Designers Guide, Ti, 1996 http://www.ti.com/lit/ml/scba010/scba010.pdf [2] Logic Guide, Ti, 2014 http://www.ti.com/lit/sg/sdyu001aa/sdyu001aa.pdf -- WBW, V.P. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
The example circuits given on that webpage will be inferior in every way to RTL and DTL logic from the 1960's, which itself is inferior to late 60's/early 70's TTL. A good reference on how to do discrete transistor logic design from the 1960's, is TI's book Transistor Circuit Design. I just poked around bitsavers hoping it might be there, but didn't see it. Paper copies abound in used bookstores. http://www.amazon.com/Transistor-Circuit-Design-Instruments-Incorporated/dp/0070637377 There are a handful of level-shifting logic-type circuits for oddball voltages that might still be done best using discrete transistors especially if you don't need say the full quad of a MC1488 or MC1489. Tim N3QE On Mon, Jun 1, 2015 at 11:00 AM, Vlad t...@patoka.org wrote: I am curious, how the integrated gates could be compared for those created on discrete elements ? Let say simple gates like this: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html Regards, Vlad On 2015-05-31 18:23, Attila Kinali wrote: On Sun, 31 May 2015 14:06:26 -0400 Dan Watson watsondani...@gmail.com wrote: Has anyone used or experimented with the 74LVC series of ICs? I have found them quite useful in projects. Supply voltage of 2-5V, and two inverters or a single gate or flip flip in a SOT package. They make for much cleaner layouts than large DIPs. Yes, quite a few of those. After CPLDs and FPGAs replaced all of the more complex 74xxx's, people realized that most projects do not need 4 NAND gates at one spot, but rather single ones here and there (a schmitt-trigger for signal conditioning, an AND gate to couple two enable lines,...). I'm wondering if they are acceptable replacements for 74HC, AC, etc in timing circuits. I have never used any of the LVC in a timing circuit, but i would guess they are not worse than the AC. Also they have the advantage of having single gates per package, which helps minimizing cross coupling between different signal paths. BTW: [1] may contain some interesting data for you. Especially as it compares different manufacturers too. Looking at [2], the ALVC family would probably be also worth a look. Attila Kinali [1] Low Voltage Logic Designers Guide, Ti, 1996 http://www.ti.com/lit/ml/scba010/scba010.pdf [2] Logic Guide, Ti, 2014 http://www.ti.com/lit/sg/sdyu001aa/sdyu001aa.pdf -- WBW, V.P. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
Moin, On Mon, 01 Jun 2015 11:00:31 -0400 Vlad t...@patoka.org wrote: I am curious, how the integrated gates could be compared for those created on discrete elements ? Let say simple gates like this: For the same implementation: Worse. There is much less control over the exact building of discrete devices than integrated ones. There hundreds of tiny things that are harder to control: * You have wires going over the PCB. These have a long length, thus a high inductivity, and high capacity. * They are on a substrate that is known to be quite hydrophile and thus has changing electrical parameters (dielectric constant, permeability, resistivity,...) * Everything is slower, due to higher capacitance/inductance/resistance of the wires inbetween. * Slower translates into less defined edges - more jitter. * Higher capacitance translates into more current flowing at the same speed, which again translates into more shot-noise (though less therma noise) * Longer wires are more susceptible to EMI, or rather pick-up of tiny interferences from other circuits or even other parts of the same circuit. * Longer wires are also more prone to emit EMI. ... just to name a few. This list can be continued for quite some time. On the other hand: A well designed discrete circuit can beat a general purpose integrated circuit in almost all performance measures. http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html These are resistor-transistor-logic (RTL) elements. Those even more noisy due to their simple build up. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
The gates on that page http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html use bipolar transistors. The 74LVC parts are CMOS. There are various effects caused by that difference. And those examples have vastly inferior control over input switching levels, compared to just about any well made digital IC from the last half century. (Funny to think that it has been half of a century!) 2N type transistors might have switching delays upwards of 100 ns (depending on load), whereas the LVC parts switch in the 1-5 ns range. On the other hand: A well designed discrete circuit can beat a general purpose integrated circuit in almost all performance measures. Some performance metrics would be hard to beat with even a well designed discrete circuit. On-die capacitance and inductance tends to be much smaller than any discrete circuit can achieve. Andy ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Performance of 74LVC series ICs
Hi, Has anyone used or experimented with the 74LVC series of ICs? I have found them quite useful in projects. Supply voltage of 2-5V, and two inverters or a single gate or flip flip in a SOT package. They make for much cleaner layouts than large DIPs. I'm wondering if they are acceptable replacements for 74HC, AC, etc in timing circuits. A couple examples of the series I'm referring to: http://www.ti.com/lit/ds/symlink/sn74lvc2g14.pdf http://www.ti.com/lit/ds/symlink/sn74lvc1g175.pdf Thanks, Dan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
Hi The 74HC series is an “old and slow” CMOS family. In some cases people use their low speed to do filtering (they won’t follow a fast glitch …). Other than that sort of thing, the AC and LVC should be fine replacements for them. The HC might pull a little less power with nothing going on. If you are running on a coin cell it’s worth checking. The 74AC series was essentially the first group of fast CMOS parts to hit the market. They were indeed fast. They also had some issues with lead frame induced glitches (power and ground pin locations …). You see a lot of odd things done to try to take care of this. Starting about 20 years ago, people began to bring out “improved” versions of the AC parts. Processes had gotten faster and people had learned some things. Within 10 years the number of different families became almost un-countable. I think these guys spent a *lot* of time coming up with weird reasons to add a new line of logic to their portfolio. The good news is that faster is better in silicon CMOS (except in weird cases like above). About all you need to check is: 1) Is it CMOS or TTL levels? (AC vs ACT , HC vs HCT, etc) get the right one. 2) Is it as fast as the stuff I’m replacing ?(check toggle rates or delay) simple answer is almost always yes if HC and AC are the “comparison standard”. 3) Will it handle my supply? Some of the newer stuff is 3.3V only. There are some odd cases like buffer gates. If you are crossing one of those, just be sure you cross it to a buffer and not to a simple inverter. Drive levels can matter. Simple answer - sure they are better / lower noise floor / better ADEV / faster / cheaper / easier to layout than the old stuff. They probably are lower power as well. Bob On May 31, 2015, at 2:06 PM, Dan Watson watsondani...@gmail.com wrote: Hi, Has anyone used or experimented with the 74LVC series of ICs? I have found them quite useful in projects. Supply voltage of 2-5V, and two inverters or a single gate or flip flip in a SOT package. They make for much cleaner layouts than large DIPs. I'm wondering if they are acceptable replacements for 74HC, AC, etc in timing circuits. A couple examples of the series I'm referring to: http://www.ti.com/lit/ds/symlink/sn74lvc2g14.pdf http://www.ti.com/lit/ds/symlink/sn74lvc1g175.pdf Thanks, Dan ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Performance of 74LVC series ICs
On Sun, 31 May 2015 14:06:26 -0400 Dan Watson watsondani...@gmail.com wrote: Has anyone used or experimented with the 74LVC series of ICs? I have found them quite useful in projects. Supply voltage of 2-5V, and two inverters or a single gate or flip flip in a SOT package. They make for much cleaner layouts than large DIPs. Yes, quite a few of those. After CPLDs and FPGAs replaced all of the more complex 74xxx's, people realized that most projects do not need 4 NAND gates at one spot, but rather single ones here and there (a schmitt-trigger for signal conditioning, an AND gate to couple two enable lines,...). I'm wondering if they are acceptable replacements for 74HC, AC, etc in timing circuits. I have never used any of the LVC in a timing circuit, but i would guess they are not worse than the AC. Also they have the advantage of having single gates per package, which helps minimizing cross coupling between different signal paths. BTW: [1] may contain some interesting data for you. Especially as it compares different manufacturers too. Looking at [2], the ALVC family would probably be also worth a look. Attila Kinali [1] Low Voltage Logic Designers Guide, Ti, 1996 http://www.ti.com/lit/ml/scba010/scba010.pdf [2] Logic Guide, Ti, 2014 http://www.ti.com/lit/sg/sdyu001aa/sdyu001aa.pdf -- _av500_ phd is easy _av500_ getting dsl is hard ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
