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TMS320F28P650DK: Watchdog Clock Configuration

STEVEN LOU
Prodigy 20 points
Part Number: TMS320F28P650DK

Tool/software:

Dear TI Team,

I'm trying to figure out how to configure the pre-divider (WDPRECLKDIV) and prescaler (WDPS) of the watchdog,
but the technical reference manual for the TMS320F28P65x lacks a use case description, as shown in Figure 1 below.

I found another chip with a similar watchdog clock design, such as the TMS320F28004x, which provides more detailed bit definitions, as shown in Figure 2 below.

Do these two chips use the same design, so that I can refer to the TMS320F28004x's manual for TMS320F28P65x's watchdog configuration?
If not, where can I find this information in the TMS320F28P65x's manual?

Figure 1. TMS320F28P65x

Figure 2. TMS320F28004x

  • 0
    TI__Mastermind 20662 points

    Hi Steven,

    You can reference the hw_sysctrl.h for both devices to see what bit-fields are supported. You can then use this list to query the driverlib files sysctrl.h and sysctrl.c to find out what supported APIs are available that write directly to these registers. Alternatively, use can use the HWREG function to write to custom fields within a register.

    Below are the following bits available in the WDCR registers

    You can also check out watchdog.h to see the list enumerations that correspond to the prescale values for the  SysCtl_WDPrescaler parameter.

    Below are the list preseclae values for the WDCLK:

    Below are the defines associated with the WD Predivider

    From looking at the snapshots above, it appears that the F28P65x TRM does not list the descriptors for those fields. And looks like the Watchdog on the F28P65x does not have a WD flag support. The watchdog reset status flag is supported within the RESC sysctrl register. See snapshot below.

    Regards,

    Ozino

  • 0 in reply to Ozino Odharo
    Prodigy 20 points

    Hello Ozino,

    Thank you for your suggestion.

    I compared the driverlib for both the F28P65x and F28004x and found that the pre-divider (WDPRECLKDIV) and prescaler (WDPS) appear to be identical.
    Since this is the case, is it correct to assume that I can use the F28004x manual to configure these two parameters for the F28P65x?

    Additionally, I noticed a slight discrepancy.
    The SysCtl_WDPrescaler in the driverlib you mentioned starts from 1, not 0.
    However, the F28004x manual indicates that 0h and 1h share the same definition.

    Can you confirm if this is also the case for the F28P65x?

    Your clarification on these points would be greatly appreciated, as it will assist with my evaluation work.

    Best regards,

    Steven

  • 0 in reply to Ozino Odharo
    Prodigy 20 points

    Hello Ozino,

    I have an additional question regarding a discrepancy I've found.

    You mentioned that the F28P65x does not support the WD flag, while the F28004x does.
    Following your suggestion, I looked at the F28004x driverlib, but I could not find a definition for the WD flag there.
    Does this indicate that F28004x does not define the WD flag in the WDCR as well?

    However, the WD flag is defined in the WDCR, according to the F28004x manual. This seems to be a contradiction.
    Could you please clarify which source I should trust for the information—the driverlib or the manual?

    Best regards,

    Steven

  • 0 in reply to STEVEN LOU
    TI__Mastermind 20662 points

    Hi Steven,

    Thank you for your patience. I do believe there is a discrepancy between the software and the TRM. I'll have the watchdog expert confirm.

    I have cross checked the bit-field equivalent code and see that the WDFLG bit-field is also not defined for the F28P65x. However it shows up in the WWD registers, shown below.

    Based on what we have looked into, I'll say that watchdog functions similarly between both devices. 

    I'm going to include the watchdog expert to comment further.

    Regards,

    Ozino

  • 0 in reply to Ozino Odharo
    Prodigy 20 points

    Hello Ozino,

    Thank you for your continued help. I'm facing some confusion and would appreciate your clarification.

    Following your latest clue about the "device_support" folder, I compared the F28P65x and F28004x files, as shown below.

    This comparison has raised a new question regarding the WDFLG bit in the WDCR register.

    I've summarized the information I've found from the three different sources in the table below:

    WDCR include WDFLG or not?
    Device TRM driverlib device_support
    F28P65x x x o
    F28004x o x x

    As the table shows, there are conflicting details. The "device_support" folder for the F28004x indicates that the WDCR does not include the WDFLG, while the F28004x's TRM states that it does. The F28P65x shows the exact opposite result.

    I'm less concerned with the exact definition of WDFLG and more focused on understanding which source is correct.
    As a customer, I would expect the TRM to contain accurate information about the chip's functionality, with software support being a separate matter.

    Given these conflicting sources, could you please advise which one I should rely on?

  • 0 in reply to STEVEN LOU
    TI__Mastermind 19085 points

    Hi Steven,

    I apologize for this discrepancy. Let me do some digging and get back to you with which is the correct source. 

    Best Regards,

    Delaney

  • 0 in reply to Delaney Woodward
    TI__Mastermind 19085 points

    Hi Steven,

    Apologies for the delay, I got held up with some other activities. The watchdog modules for F28004x and F28P65x are listed as the same type in the peripheral user guide, so they should function similarly.

    For the WDFLG bit, it looks like some issues were found with the design implementation in WDCR and the documentation ended up removing the flag to avoid having customers use it. They most likely forgot to remove it from the software or left it in/put it back for ease-of-migration purposes.

    For the enumerations of WDPS, I'm having trouble finding how those are being sourced in the TRM. Let me consult the software team to understand more and I will get back to you.

    Sorry for all the confusion here.

    Best Regards,

    Delaney 

  • 0 in reply to Delaney Woodward
    Prodigy 20 points

    Hello Delaney,

    Thanks for your help with this.

    Based on your reply, I want to clarify a point to ensure I'm on the right track.
    Is it correct that the WDCR register's bit-field definition is the same for both the F28004x and F28P65x, with the WDFLG (bit 7) being the sole difference?

    If that's the case, since the F28004x TRM is more detailed, does it mean I can reliably use it to configure the watchdog's pre-divider (WDPRECLKDIV) and prescaler (WDPS) for the F28P65x?

    Best regards,

    Steven

  • 0 in reply to STEVEN LOU
    TI__Mastermind 19085 points

    Hi Steven,

    I am still confirming if the fields have the same meaning on both devices. I will get back to you in the next 1-2 days after I have talked more to the software and design teams.

    Best Regards,

    Delaney

  • 0 in reply to Delaney Woodward
    TI__Mastermind 19085 points

    Hi Steven,

    To update, I am still trying to track down the reasoning behind this and confirm if the design implementations are the same across the devices. I apologize that this is taking me so long.

    Best Regards,

    Delaney