• State Resolved
  • Locked Locked
  • Replies 17 replies
  • Subscribers 32 subscribers
  • Views 1316 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

High end timer performance

Dan S17
Expert 1510 points
Other Parts Discussed in Thread: HALCOGEN

Hello


I have not been able to find any information regarding the performance of the High End Timer on the Hercules board. In particular I would like to know the stability and accuracy of the timers. Can some body point me in the right direction?


Thank you,

Dan

  • 0
    TI__Guru 59540 points

    Hi Dan,

    I have forwarded your inquiry to one of our NHET experts. They should get back with you soon.

  • 0 in reply to Chuck Davenport
    TI__Guru**** 191216 points

    Hi Dan,

      For PWM generation, the NHET can generate a minimum pulse width to one high resolution clock provided that the period of the PWM signal is minimum of 2 loop resolution clocks. One high resolution clock can be as small as one VCLK2 clock cycle. Depending on which Hercules device you have, for example, you might be able to configure the VCLK2 equal to 100MHz and the minimum pulse width can be as small as 10ns. For input capture, the minimum period that can be measured is 1 loop resolution clock plus 2 VCLK2 cycles and the minimum pulse width high or low is 2 high resolution clocks plus VCLK2 clocks.

  • 0 in reply to Charles Tsai
    Expert 1510 points

    Hello Charles


    What can you provide me with the following information for the main oscillator of the Hercules board?

    (1) Is it a RC oscillator or a crystal oscillator?

    (2) Is it internal or external to the microcontroller?

    (3) If external then is it part of the high-end-timer unit or a separate crystal?

    (4) What Is the stability and accuracy of the oscillator?

    (5) If the main oscillator does not meet my needs with respect to stability and accuracy can an external oscillator be easily connected to the Hercules board?


    Thank you,

    Daniel

  • 0 in reply to Dan S17
    Guru 15740 points

    Hi Daniel,

    What Hercules board do you refer to? The LaunchPad or an other  evaluation board?

  • 0 in reply to Jan Cumps
    TI__Guru**** 191216 points

    Hello Dan,

      Below are the answers.

    (1) Is it a RC oscillator or a crystal oscillator?

    crystal oscillator for the main oscillator

    (2) Is it internal or external to the microcontroller?

    External

    (3) If external then is it part of the high-end-timer unit or a separate crystal?

    Separate crystal. High End Timer is an internal module inside the microcontroller.  The crystal oscillator is used as the clock source to the internal PLL inside the uC. The PLL output is further divided to generate various clock domains inside the uC including the VCLK2 for which the High End Timer module uses as the reference clock.

    (4) What Is the stability and accuracy of the oscillator?

    Accuracy of the crystal is about 30ppm.

    (5) If the main oscillator does not meet my needs with respect to stability and accuracy can an external oscillator be easily connected to the Hercules board?

    As noted, external crystal is used on the board.

  • 0 in reply to Jan Cumps
    Expert 1510 points

    Hi Jan


    Thanks. I am referring to the LaunchPad.


    Daniel

  • 0 in reply to Charles Tsai
    Expert 1510 points

    Hi Charles


    Thanks you very much for your answers to my questions concerning the Hercules LaunchPad. I have three more questions:


    (1) Could you answer the same questions for the C2000 LaunchPad?

    (2) If I wanted to replace the external crystal oscillator with a more stable oscillator would it be straightforward?

    (3) If I wanted to use a more stable oscillator is there one that you could recommend?


    Thank you soooo much!

    Daniel

  • 0 in reply to Dan S17
    Guru 15740 points

    I have that one too. The version with the TMS570LS04x µController.

    The schematics for that kit are available on-line.

    The oscillator is on page 5. In the BOM (available in the eagle archive) we can see that the processor crystal  Y2 is 16 MHz

    1 Y2 16M 7M-16.000MAAJ-T TXC 3.2*2.5mm

    In HALCoGen, you can look at the different timings in the clock tree tab:

  • 0 in reply to Jan Cumps
    TI__Guru**** 191216 points

    Hello Dan,

      First also thanks to Jan for showing the HalcoGen setup and the schematic of the launchpad http://processors.wiki.ti.com/images/7/79/Hercules_LaunchPad_Sch.pdf.

     For C2000 launchpad and any general C2000 support please post your questions in the C2000 Forum so they can provide more detailed responses.

    In the LS04x lanuchpad there is a J1 jumper that you can use to provide an external clock to the OSCIN input of the uC. Please refer to the schematic.

      What type of tolerance on the crystal are you looking for that the existing onboard crystal can not meet your requirement and applications? I don't know what to recommend at the moment.

     

     

  • 0 in reply to Jan Cumps
    Expert 1510 points

    Thanks Jan! i was just now trying to find the schematics. Cool!!

  • 0 in reply to Charles Tsai
    Expert 1510 points

    Hi Charles


    The stability of the crystal (30 ppm) is probably good enough for my application. What can you tell me about the accuracy of the oscillator and clock? In my application I need to determine the time between events and I need better than millisecond accuracy. Is calibration needed?


    Cheers,

    Daniel

  • 0 in reply to Dan S17
    TI__Guru**** 191216 points

    HI Dan,

      For High End Timer  the high resolution clock is the smallest time increment with which a pin can change it’s state or can be measured in the case of input signals.  The time between two events that you are trying to measure will be in term of number of high resolution clocks. As I explained before one high resolution clock can be configured to equal to one VCLK2.  For LS04x device the VCLK2 can be as fast as 80MHz or 12.5ns clock cycle. So the accuracy of the NHET will be in the granularity increment of 12.5ns.

  • 0 in reply to Charles Tsai
    Expert 1510 points

    Hi Charles

    Ostensibly a crystal would oscillate at the specified frequency but often they are in error a bit due to manufacturing specifications and precision. Do you have any data on the crystal used or could you tell me which crystal it is?

    Thanks again,

    Daniel

  • 0 in reply to Dan S17
    Guru 15740 points

    The BOM lists the part number.

    it's this one: TCX 7M-16.000MAAJ-T

    According to the data sheet attached to that page:

    Frequency tolerance at 25 °C: +- 30 ppm

    Frequency stability between -20 and +70 °C: +- 30 ppm

    Max aging per year at 25 °C: 3 ppm

  • 0 in reply to Jan Cumps
    TI__Guru**** 191216 points

    Hi Dan,

       It is as stated by Jan in the previous reply,. The datasheet can be found at this link.

    http://www.txccrystal.com/images/pdf/7m.pdf

     

  • 0 in reply to Charles Tsai
    Expert 1510 points

    Thank you, Jan and Charles. I will take a closer look at the datasheet.

  • 0
    Guru 15740 points

    Dan,

    I have a Hercules LaunchPad at home. Is there a particular test that you are looking for?

    If you need high precision verification, I'll have to pass, but I have measure equipment that covers the 80 MHz frequency of the LaunchPad.