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TMS320F280049M: CMPSS Analog Group Connection

Kengo Furuya
Expert 7650 points

Part Number: TMS320F280049M

Hello,

I checked Figure 5-25. Analog Group Connections in the datasheet, and have some questions

1. The initial value of CMPHPMXSEL and CMPLPMXSEL are 0, and CMPx_HP0、CMPx_LP0 is selected. 

At the time, is the input status of the comparator high impedance?

I worry that unused CMPSS1_CTRIPL is set by XBARFLG1. In this case, should DACxVALA be set 0x0FFF?

2. I understand PGARFILTER path is not available. When disable it, is there no effect to CMPx_HP0、CMPx_LP0?

Regards,

Furuya

  • 0
    TI__Mastermind 28275 points
    Hi Kengo,

    When CMPx_HP0 or CMPx_LP0 is selected, PGA_OF is fed to the comparator. PGA_OF also comes out on a pin so the signal fed to the comparator will be whatever signal is on PGA_OF pin irrespective of whether the PGARFILTER is enabled or not.

    Yes, if you are using only COMPL or COMPH in the CMPSS module, you should max out the DACVAL of the unused comparator to prevent spurious trips.
  • 0 in reply to Frank Ankapong
    TI__Expert 7650 points

    Frank,

    Thank you for your answer. For PGA RFILTER path, the following note is there on the datasheet.

    C. The PGA RFILTER path is not available on some device revisions. See the TMS320F28004x Piccolo Microcontrollers Silicon Errata for more information.

    Does it mean that (C) path is always disconnected, or connected but cannot enable Rfilter? 

    Regards,

    Furuya

  • 0 in reply to Kengo Furuya
    TI__Mastermind 28275 points

    Furuya,

    The wording for 'C' could be improved. What it means is the PGA RFILTER path is not supported on some device revisions. On reset, the PGA RFILTER path is disabled and will have to be enabled using the register settings. The path is still there but just not supported on some revisions.