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TMS320F280049C: TMS320F280049C

Selec Controls1
Intellectual 280 points

Part Number: TMS320F280049C

In ADC their is a PPB block in that their is a register LIMITHI and LIMITLO  what values we should put in that?

Based on PPB please provide one example on of Zerocrossing using PPB. 

  • 0
    TI__Mastermind 40540 points

    Hi,

    You can put any limits you want depending on how far off the PPBRESULT is.  For example, say you are monitoring a signal that is on the average around 1.5V but sometimes signal can fluctuate by 100mv (1.5V+/-100mV),  which is still acceptable but you want to take an action when signal is above 1.6V or below 1.4V.  This is where PPB TRIPHI/TRIPLO feature will come in handy.  Assuming the external VREF is 3.0V, you can set the TRIPHI limit to 2184 (digital value for 1.6V with 3V VREF) and TRIPLO limit to 1911 (digital value for 1.4V with 3V VREF).  See example adc_ex8_ppb_limit for the implementation but note in the example that limits are set to 3000 and 1000.

    There is no example for the zero crossing since implementation is straightforward.  With zero crossing, as soon as PPBRESULT crosses the 0 value (example: PPBRESULT progressively decreases  by 10LSBs every after conversion like 102,92,82....22,12,0, -2).  When it PPBRESULT crosses from 0 to -2, and ADCEVTSEL.PPBxZERO is set to 1, then it will detect this crossing.  Also note that with PPBRESULT, it is possible to get a negative result with the subtraction of ADCPPBxOFFREF.

    Regards,

    Joseph