...I ought to add that I've built the circuit with 74HC4040Ns and (you guessed it!) it doesn't work...hmmm. Not unusual I agree but I've checked this simple circuit a hundred times, watched the transistion of the pulses from a parallel port and nothing but nothing seems to trip the Q outputs to the correct states even though the clock and reset lines appear to do what they're supposed to.
Of course, there may simply be a wrong connection/solder bridge/etc but AFAIK it's clean and wired as it should be. I've even swapped out the 74HC4040Ns for two others (had a bunch of them lying around) but to no avail.
What is the maximum voltage reached by the parallel port output pulses? CMOS parts need to see voltages close to the power rail, while the parallel port is probably assumed to be OK with TTL-level voltages.
TTL parts into CMOS often works, but it often doesn't -- you should check what you're getting, and what the 74HC4040 wants.
HC105 FIFO is improved , you can circulate it and still be tri-state ...
BTW ,,,anyone study Speed-pow pdt ? What is the bad stuff ? What dont work at 3.3vdc , ultra effecient ? Notice the pitfalls , now , on SRAM S-P pdt! You can buy SRAM thats less than 1 Mili-W per mhz , but you can buy 50 MilliWatt from JameCo .
? Has anyone got any recent bad experiences.
Notice DRAM is evolving into PSRAM . They have improved DRAM , so much , it will kill SRAM . It uses about .0001 amps to refresh.
Im doin ARM , free OpSys . No English , No ASCII , no bloat ( loads at 8KB ) .
I don't see any decoupling caps in there. If true then that ain't good. Place a 0.1uF ceramic next to each chip, shortest possible connection from VCC to ground (here it's called VSS). Also one at the output of the
7805. Might also need a 47uF or 100uF electrolytic at that point but I don't know what the parallel port would say to its surge current.
CD4000 series chips are much slower and they can occasionally live without decoupling caps. It's still better to have them. 74HC definitely needs them.
Tim: pulses at 5v which, on the clock and reset lines appear to be 'working' -- ie the reset is pulled low or else is at 5v, similarly the clock, but the clock doesn't trip the Qs and the reset doesn't reset 'em! (At least, not with any -- excuse the pun -- logic).
Rich: so put pullup resistors of between 4k7 and 10k across lines going to the clock and reset? I'll try it...
Joerg: no decoupling caps at the moment but I think I can dig a few out of my junkbox to try it.
Thanks everyone. I'll try the above and report back
For some values of "do". I'm just working on getting a couple of companies into a partnership for sourcing and supporting some specialized high-precision mechanical stuff from there at the moment. I have not visited Formosa for a while now. 8-(
Some semiconductor prices will vary signficantly by geographic location, but you can't always be sure they'll be less until you see the quotes.
Try the ROC and the PRC. ST may be dumping parts there and/or the price structure may be flatter.
Best regards, Spehro Pefhany
"it\'s the network..." "The Journey is the reward"
email@example.com Info for manufacturers: http://www.trexon.com
I have had difficulties with some brands of 74HC4060's (which are similar to but not identical to the 4040).
In particular, the problem was that in some makers' 74HC4060's, the built-in oscillator didn't oscillate reliably. I ended up just specing the good old CD4060 which in my particular case does oscillate reliably.
All that said, except for using "analog" sections in digital parts (the oldtimes all know that all digital parts are made of analog parts!) I've never had a problem when the only power supply was 5V anyway.
Like any digital circuit using counters, you'll want at least some bypassing and good construction techniques to make the circuit reliable. CMOS (either CD40xx or 74HC40xx) is so much more forgiving than regular TTL. And if the original circuit doesn't really work, then the transliterated one won't work either :-).
I presume the problem ones weren't Toshiba. All the 74HC4040's I've ever used came from Tosh, and nary a problem.
What I HAVE expereinced recently though was a CD4017 problem. Two prototype products were built, one with Philips and one TI. No issues. Built ten pre-prod units with a mixture of ST and ON-Semi 4017's. Four had repeatable failures in a certain test. Those four had ST 4017's, the six without problems were the ON-Semi-e quipped.
I hate it when a simple part of a project - in this case a 4017 driving an input on a 4174 - is manufacturer-dependent.