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Pulsout questions — Parallax Forums

Pulsout questions

Buck RogersBuck Rogers Posts: 2,190
in BASIC Stamp
Hello!
New project time, and I decided to make use of my BASIC Stamp investment.

Simple one here, can the pulse output instruction be configured to produce a 15ns pulse width? The thing it is going to usually insists on a 25Mhz clock frequency, but that's a bit much for the Stamp. I normally run it on a decidedly slower clock produced via an optical sensor previously made by TI, a TSL220 device as it happens, but for what I'm doing with the output, I'm interested in having the Stamp do most of lifting here.

Incidentally I selected a Stamp One here first.

Comments

  • kwinnkwinn Posts: 8,697
    Not sure on exactly what you have in mind, but assuming a square wave from the clock oscillator you would need a 33.333...MHz clock to get a 15nS pulse, and that's assuming there was some hardware there to output the clock signal to a pin. I would guess this is not possible with a Basic Stamp.
  • Buck RogersBuck Rogers Posts: 2,190
    And I agree.

    I was planning on updating my original to indicate that the Stamp One was being ruled out because of how the project carrier board was connected. Typically that (formerly) TI Optical part would run at about the right burst I needed, but not necessarily the frequency. I'll needed to do some tests before I make any definite decisions, but the Stamp will still be considered. Take a look at the attached data sheet for my reasons.
    PDF
    PDF
    TSL220.PDF
    153K
  • kwinnkwinn Posts: 8,697
    After looking at the basic stamp comparison chart it looks like the only stamps with a clock frequency high enough to come close to having a 15nS pulse output would be the BS2SX-IC (50MHz) and possibly the BS2PX24 (32MHz). Even so, it would need assembly, not PBasic, and on chip hardware to output the clock signal in the case of the PX24.

    Why the requirement for a 15nS pulse, and how frequently does it need to be produced?
  • Buck RogersBuck Rogers Posts: 2,190
    kwinn wrote: »
    After looking at the basic stamp comparison chart it looks like the only stamps with a clock frequency high enough to come close to having a 15nS pulse output would be the BS2SX-IC (50MHz) and possibly the BS2PX24 (32MHz). Even so, it would need assembly, not PBasic, and on chip hardware to output the clock signal in the case of the PX24.

    Why the requirement for a 15nS pulse, and how frequently does it need to be produced?

    Hello!
    Take a look at the data sheet for the SN74167 part as attached. It has that interesting requirement. Both it and the SN7497 (Not attached) respond accordingly. Typically the parts find themselves being used to translate a binary or binary coded decimal in the case of the SN74167 into an appropriate pulse stream. For what I've got next in mind I had thought of having the Stamp produce the clock pulse that would be then translated as appropriately.

    Then it falls upon the Stamp to accept the stream and then display it appropriately. Either as characters using the standard Alphanumeric LCD displays we are used to. Or using the Prop Back Pack device as a video stream.

    We'll see what does happen, but I do appreciate your input.
    pdf
    pdf
    sn74167.pdf
    296K
  • kwinnkwinn Posts: 8,697
    That seems like an extremely roundabout way of reading in a 4 bit BCD value, and if you are using the BS2 to control all the inputs to the 74167 you need five pins, so no gain over reading in the 4 bit BCD data directly. Also much (at least 10x) slower. The decade rate multiplier requires 10 clock pulses to output the number of pulses set by the B0 to B3 rate input bits.
  • kwinnkwinn Posts: 8,697
    No reason the BS2 cannot do this however. The signals in to the 74167 do not have any minimum input time requirement.
  • Buck RogersBuck Rogers Posts: 2,190
    kwinn wrote: »
    No reason the BS2 cannot do this however. The signals in to the 74167 do not have any minimum input time requirement.

    Hello!
    Okay, but the bit control signals, which the truth tables use for deciding the appropriate rates would be preset using different DIP switch settings.

    Meanwhile I'm still working on the details, including what's happening and why.

    Appreciate the help of course.
  • kwinnkwinn Posts: 8,697
    Buck Rogers wrote: »
    kwinn wrote: »
    No reason the BS2 cannot do this however. The signals in to the 74167 do not have any minimum input time requirement.

    Hello!
    Okay, but the bit control signals, which the truth tables use for deciding the appropriate rates would be preset using different DIP switch settings.

    Meanwhile I'm still working on the details, including what's happening and why.

    Appreciate the help of course.

    Dip switches and pullups on the B0-B3 inputs would work for figuring out the details. Of course so would looking at the gate inputs/outputs working back from the output of the 4 input or gate to the flip/flops.
  • E_TexasTeslaE_TexasTesla Posts: 15
    Possible Voltage to frequency ic controlled by the stamp.
    https://www.analog.com/media/en/technical-documentation/application-notes/an14f.pdf
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