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Signal breakage at the NHET PIN 10

Bindu Tanguturi
Expert 1180 points

Other Parts Discussed in Thread: TMS570LS20216

I am using the TMS570 Microcontroller Development Stick, with a TMS570LS20216 MCU.

I have developed the small application which read the fequency of input square wave signal available on the pin 10.

I have followed the SPNA130A–September 2011 application note to this task. But i have used the circular buffer mode

and storing the 100 Frames. It is working fine.

 

Now i need to update my program to add the following feature.

 

"If there is any breakage in the input signal, my application should report an error."

 

During update to my application, i come across below doubts.

 

Test Setup : I have the signal generator which sends the maximum frequecy of 12.5MHz.

 

 

1. I am measuring the time period between the FALL and FALL. During real time, if some how signal does not become low after the previous FALL, how to find

the break in the signal ?

 

My understanding : During this time, the PCNT Data Filed will not be updated (data vaiable in buffer HTU buffer also will not be updated) and the period

count in the Control Filed will reache to 0x1FFFFFF. With the LRP setting to 914ns, it takes approximately 30 seconds to reach this value. So if check this

filed in my application, it take approximately 30 seconds to report this error. If i change the LRP it may come to approximately 2 seconds. But as per my

requirement i need to report within 200ms. Suggest me for any other way and confirm whether my understanding is correct or not.

 

2. The request type in the PCNT instrution is GENREQ. What does it mean ? More explanation on request type please.

 

3. What is the trigger event ? I mean when the data will be copied from NHET RAM to main memory Buffers ? How the HTU knows that

new data is available in the NHET RAM ?

 

[It would be easy if there is a way to know that when was the last time data coped from NHET RAM to main memory]

  • 0
    Expert 1180 points

    Can anyone respond please.

  • 0
    TI__Genius 14205 points

    Hi Bindu,

    I have forwarded your query to our HET expert. We will get back to you as soon as possible.

    Best Regards
    Prathap

  • 0 in reply to Prathap
    Expert 1180 points

    Thanks Prathap. I am waiting for your response.

  • 0 in reply to Bindu Tanguturi
    TI__Genius 14205 points

    While we are waiting for the experts comments I have few points to help you.. Please find them in Bold letters

    1. I am measuring the time period between the FALL and FALL. During real time, if some how signal does not become low after the previous FALL, how to find
    the break in the signal ?
     
    My understanding : During this time, the PCNT Data Filed will not be updated (data vaiable in buffer HTU buffer also will not be updated) and the period
    count in the Control Filed will reache to 0x1FFFFFF. With the LRP setting to 914ns, it takes approximately 30 seconds to reach this value. So if check this
    filed in my application, it take approximately 30 seconds to report this error. If i change the LRP it may come to approximately 2 seconds. But as per my
    requirement i need to report within 200ms. Suggest me for any other way and confirm whether my understanding is correct or not.

    --- Use MCMP/ECMP after PCNT instruction using register A and the set a Data value according to what time frame you want to do action.. You can enable Interrupt if you want to trigger interrupt when this scenario occurs.

    2. The request type in the PCNT instrution is GENREQ. What does it mean ? More explanation on request type please.

    --- 8 Request are present in NHET which can be configured to sent either DMA request or HTU request. It is hard coded, please refer "section 18.4.8 NHET Requests to DMA and HTU" for more info along with device data sheet for DMA request assignment.
     
    3. What is the trigger event ? I mean when the data will be copied from NHET RAM to main memory Buffers ? How the HTU knows that new data is available in the NHET RAM?

    --- I guess trigger event you are refering to GENREQ. Once a request(assuming DMA here) is generated by an instruction, If respective DMA channel is already configured in DMA module with source as your NHET buffer and destination as System memory, your job is taken care.
     
    [It would be easy if there is a way to know that when was the last time data coped from NHET RAM to main memory]

  • 0 in reply to Prathap
    Expert 1180 points

    Thanks Prathap.

    My question is when the request will be generated by instruction ? And what is the GENREQ request type ?

  • 0 in reply to Bindu Tanguturi
    TI__Genius 14205 points

    Hi Bindu,

    To have better explanation let me take an instruction ECMP. ECMP can generate interrupt(irq bit in the instruction) and generate request ( Request type bits (C27&C28).
    1) If IRQ bit is enabled - when a compare occurs ( i.e Z flag is set), HET will generate an interrupt to the system, As a regular interrupt it has to be serviced.
    2) If request is selected as GENREQ, and if you have configured either DMA or HTU, it generates a trigger / request to DMA or HTU to either do a data read or write it depends on the useage.

    I would encourage you to go through the "Execution" section below every Instruction for clear picture.

    Best Regards
    Prathap