Shop OBEX P1 Docs P2 Docs Learn Events
CPLD 24 pins — Parallax Forums

CPLD 24 pins

AEObiAEObi Posts: 4
edited 2014-06-19 12:50 in General Discussion
hi all

I'm currently updating an old project. It used to have a PALCE22v10 chip from Cypress. It was then replaced with a ATF750CL which is not working now quite as well as I hoped.
Can anyone recommend a CPLD ?
I've been trying to find 24 pin, 5V Vcc CPLD's with Schmitt triggers for the past few days but it seems like 24 pins are dying out? As well as 5V supply? Most chips are now running on 3.3V or lower with 44 or more pins.
Is this true?

Any inputs will be greatly appreciated

Comments

  • NWCCTVNWCCTV Posts: 3,629
    edited 2014-06-18 20:49
    Not sure if it is what you are looking for, but I Googled CPLD 24 pins and got several items to come up.
  • jmgjmg Posts: 15,173
    edited 2014-06-18 22:59
    AEObi wrote: »
    hi all
    I'm currently updating an old project. It used to have a PALCE22v10 chip from Cypress. It was then replaced with a ATF750CL which is not working now quite as well as I hoped.

    What package, and how is not working as you hoped ?
    The ATF750CL needs external schmitts, and careful decoupling, and the ATF750C has less noise on Vcc, as it removes the Power-save pulsing.

    AEObi wrote: »
    Can anyone recommend a CPLD ?
    I've been trying to find 24 pin, 5V Vcc CPLD's with Schmitt triggers for the past few days but it seems like 24 pins are dying out? As well as 5V supply? Most chips are now running on 3.3V or lower with 44 or more pins.
    Is this true?

    Schmitt and 24 pins is a rare combination - IIRC only PEEL22LV10CZ ?) had schmitt options and they have EOL for a long time now.

    If you want 5V, and easy to use, then ATF1502ASL/ATF1504ASL/ATF1504ASVL are the best.
    (can be programmed with FT2232H MINI MODULE)

    Above that, the Lattice MachXO2 are probably a good next step. (3v3 only)
    eg a LCMXO2-256HC-6SG32C (QFN32) could mount on a DIP24-600 breakout for an interesting item ?

    google finds this one, cute,
    http://www.ah-ed.de/catalog/modules-ahed-mach-xo2-fpga-break-out-board-p-30.html

    and if you do not need production volumes, there is always an all in 1 module/breakout.
    LCMXO2-7000HE-B-EVN

    addit: Or if the logic is quite simple, then worth a look are the GreenPAK (Wide Vcc OTP tiny parts) from
    http://www.silego.com/
  • AEObiAEObi Posts: 4
    edited 2014-06-19 00:19
    What package, and how is not working as you hoped ?
    The ATF750CL needs external schmitts, and careful decoupling, and the ATF750C has less noise on Vcc, as it removes the Power-save pulsing
    .

    It's the DIP package. The PALC22V10D worked fine, i gave the chip it's inputs and the correct results were achieved. With the ATF750CL and using the same program logic it does not respond correctly. When an input is pulled high the correct output is pulled high but when the input is removed the output remains high. I had a suspicion that it might be the pin-keeper that was not set, but according to the data-sheet and the program it is disabled. Does this pin work on the low power version or is it only on the ATF750C?

    Thank you for the rest of the information. Will look into all of them. It would be ideal if I could find a 'drop in replacement' that works to avoid having to redo the PCB layout.
    I'll see what I can find. :smile:
  • jmgjmg Posts: 15,173
    edited 2014-06-19 00:49
    AEObi wrote: »
    With the ATF750CL and using the same program logic it does not respond correctly. When an input is pulled high the correct output is pulled high but when the input is removed the output remains high.

    You can check that with a scope probe or meter.
    Is the pin keeper is on, you do need to drive both ways, and the 750CL likes fast edges.

    If the PALC22V10D works, why not use ATF22V10/ATF22LV10 variants.
    (ATF22LV10CQZ if you want low power )
  • AEObiAEObi Posts: 4
    edited 2014-06-19 01:24
    jmg wrote: »
    You can check that with a scope probe or meter.
    Is the pin keeper is on, you do need to drive both ways, and the 750CL likes fast edges.

    If the PALC22V10D works, why not use ATF22V10/ATF22LV10 variants.
    (ATF22LV10CQZ if you want low power )
    I will test the Circuit with a scope to make sure,the pin keeper should be off.

    I just looked at the ATF22LV10CQZ and it seems slower than the 750CL. Is this correct? Sorry for the stupid questions but I am new to this and want to learn how to properly compare CPLD's
  • jmgjmg Posts: 15,173
    edited 2014-06-19 02:38
    AEObi wrote: »
    I just looked at the ATF22LV10CQZ and it seems slower than the 750CL. Is this correct?
    Yes, the lower Vcc and Zero power, and lower peak power all drop the speed.
    In most SPLD apps, that is not usually critical. Faster 22V10 are available, with higher Icc.
  • AEObiAEObi Posts: 4
    edited 2014-06-19 02:50
    So if the problem does turn out to be that the edges are to slow for the 750CL, wil the 22LV10 perhaps work better?
    The problem with the PLAC22V10 was that it used to much power, so the low power 22LV10 might be a good fit
  • jmgjmg Posts: 15,173
    edited 2014-06-19 12:50
    AEObi wrote: »
    So if the problem does turn out to be that the edges are to slow for the 750CL, wil the 22LV10 perhaps work better?
    The problem with the PLAC22V10 was that it used to much power, so the low power 22LV10 might be a good fit
    What clock speed are you using, and what edge slew rates ?
    The ATF22LV10CQZ will be lower power, and from memory it has better slew tolerance, but still has issues on very slow edges.
    Because of how the part works, with a wake-up monostable, I think if you do clock it continually, on a state engine basis, then edge effects are more tolerated. ( ie any edge missed, is updates on the next clock)

    ( A shame schmitt inputs were not thought about way back when...)
Sign In or Register to comment.