| Jez Smith 06/17/12 13:33 Read: 240 times Birmingham England |
#187757 - glurk Responding to: Jim Granville's previous message |
You'll find that unless you force it not, to any logic compiler will delete strings of gates because they don't actually do anything useful as far as the compiler is concerned, its like saying a==not(not(not(not(not(not(not(b)))))));
So you have to set a flag on those gates saying do not delete, or something similar, and the delay will be astonishingly unpredictable. There is a technique called Venier timing which will allow you to measure time intervals with arbitrary precision, and it what is used in high end frequency meters/function generators.Also all the cool kids use LFSRs to generate large counters in FPGAs, they don't slow down with size unlike straight binary counters and take a minimal amount of logic. having spent some time trying to stop logic compilers from removing redundant logic I can tell you its no fun and the results can confuse the place and route tools. |
| Topic | Author | Date |
| DSO for cheap! | Joseph Hebert | 05/11/12 13:35 |
| very good | Mahmood Elnasser | 05/11/12 14:14 |
| Limitations | Joseph Hebert | 05/12/12 09:49 |
| test results | Mahmood Elnasser | 05/12/12 12:46 |
| That's valuable information | Joseph Hebert | 05/12/12 13:30 |
| well, the fact is .. | Richard Erlacher | 06/03/12 11:43 |
| tektronix 475 comparison | Mahmood Elnasser | 06/07/12 10:37 |
| Really? Why? | Richard Erlacher | 06/07/12 14:51 |
| another double post ... sorry | Richard Erlacher | 06/07/12 14:51 |
| I think ... | Erik Malund | 05/11/12 14:34 |
| Application dependant | Mahmood Elnasser | 05/12/12 05:55 |
| Indeed | Andy Neil | 05/12/12 09:10 |
| It's still too low a bandwidth, wouldn't you say? | Richard Erlacher | 06/03/12 11:50 |
| just curious, Joe could you try | Erik Malund | 05/11/12 14:36 |
| Unusual with short pulses for hobbyist projects | Per Westermark | 05/11/12 14:53 |
| is the clock running? | Erik Malund | 05/11/12 16:01 |
| Sorry, but no I can't. | Joseph Hebert | 05/11/12 16:42 |
| 10nSec Pulse | Mahmood Elnasser | 05/12/12 12:59 |
| "at random" means what exactly ? | Jim Granville | 05/13/12 18:41 |
| Answers | Mahmood Elnasser | 05/14/12 07:41 |
| more observations | Mahmood Elnasser | 06/03/12 10:51 |
| It may not be the sample rate ... | Richard Erlacher | 06/07/12 15:07 |
| digital vs analog | Mahmood Elnasser | 06/08/12 15:34 |
| Don't get me wrong, here ... | Richard Erlacher | 06/08/12 21:34 |
| poor mans's scope | Mahmood Elnasser | 06/09/12 02:01 |
| Doesn't it depend on what THEY mean by bandwidth? | Richard Erlacher | 06/09/12 20:58 |
| 20 nsec steps | Mahmood Elnasser | 06/09/12 23:08 |
| Well, one thing at a time ... | Richard Erlacher | 06/10/12 11:43 |
| Impulse Tests are better | Jim Granville | 06/10/12 16:49 |
| more capable scope | Mahmood Elnasser | 06/11/12 14:03 |
| I must have missed a step ... | Richard Erlacher | 06/12/12 08:07 |
| TEK475 | Mahmood Elnasser | 06/12/12 16:16 |
| here's another alternative ... | Richard Erlacher | 06/12/12 22:16 |
| DAC and pot in parallel? | Per Westermark | 06/13/12 01:07 |
| Logically, not physically | Richard Erlacher | 06/13/12 07:57 |
| new theory | Mahmood Elnasser | 06/14/12 00:57 |
| 3MHz is rather poor Bandwidth ? | Jim Granville | 05/11/12 16:51 |
| ordinary | Erik Malund | 05/11/12 17:20 |
| Ther are many params needed | Jim Granville | 05/11/12 18:21 |
| "only" $200 ? | Andy Neil | 05/11/12 23:59 |
| Low cost oscilloscopes | Andy Neil | 05/12/12 09:18 |
| £291 > 2*($199) | Joseph Hebert | 05/12/12 09:45 |
| It doesn't always work that way | Andy Neil | 05/12/12 10:48 |
| Once upon a time ... | Joseph Hebert | 05/12/12 13:28 |
| SDS8202 | Mahmood Elnasser | 06/14/12 13:58 |
| Read all the "fine print' first ... and ask any questions | Richard Erlacher | 06/14/12 20:31 |
| bought it | Mahmood Elnasser | 06/16/12 03:07 |
| Please let us know how this works out for you | Richard Erlacher | 06/16/12 04:19 |
| datasheet | Mahmood Elnasser | 06/16/12 05:26 |
| 2mV/div - but min trig level? | Per Westermark | 06/16/12 07:01 |
| Tests | Mahmood Elnasser | 06/16/12 09:55 |
| 24ns | Per Westermark | 06/16/12 11:09 |
| and that's the crux | Erik Malund | 06/16/12 11:41 |
| FPGA pulse Expander (edited) | Mahmood Elnasser | 06/16/12 12:06 |
some love the mother, some love the daughter  | Erik Malund | 06/16/12 12:13 |
| Here's omne fairly simple thing ... | Richard Erlacher | 06/16/12 15:22 |
| self calibtrate? | Jim Granville | 06/16/12 20:42 |
| interesting | Mahmood Elnasser | 06/16/12 23:01 |
| yes | Jim Granville | 06/16/12 23:15 |
| glurk | Jez Smith | 06/17/12 13:33 |
| DCMs | Mahmood Elnasser | 06/17/12 14:49 |
| Well.... | Jez Smith | 06/17/12 15:48 |
| I don't know where you're going with this ... | Richard Erlacher | 06/17/12 21:25 |
| xxxxx | Mahmood Elnasser | 06/20/12 12:53 |
| 333ps | Mahmood Elnasser | 06/18/12 00:59 |
| SDS9302 | Mahmood Elnasser | 07/05/12 10:32 |
| So, how are you exercising this new 'scope? | Richard Erlacher | 07/05/12 10:53 |
| so far so good | Mahmood Elnasser | 07/08/12 09:45 |
| So far so good ... | Richard Erlacher | 07/08/12 10:49 |
| rise time | Mahmood Elnasser | 08/15/12 13:28 |
| The rise time indicates that high frequencies gets dampened | Per Westermark | 08/15/12 16:26 |
| What does "bandwidth" mean? | Richard Erlacher | 08/15/12 17:45 |
| good test | Mahmood Elnasser | 08/30/12 15:09 |
Perhaps you should repeat the test ...  | Richard Erlacher | 08/30/12 23:08 |