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TMS320F28P650SK: The PPB oversampling function.

Luke Chen
Expert 5090 points
Part Number: TMS320F28P650SK

Tool/software:

Hi champs,

If we set ADCPPBxLIMIT to 4, means that we want to average four ADCPPBxRESULTs. Here are the questions,

  1. Does PPB load ADCPPBxPSUM into ADCPPBxSUM only when ADCPPBxPCOUNT is equal to ADCPPBxLIMIT?
  2. When will ADCPPBxPSUM be cleared and ready to accumulate new ADCPPBxRESULT?
  3. I use the table below to represent the contents of each register after every ADC EOC. Are the contents of this table correct?

ADCPPBxLIMIT

4

4

4

4

4

4

4

4

4

ADCPPBxPCOUNT

N/A

1

2

3

4

1

2

3

4

ADCPPBxSUM

N/A

N/A

N/A

N/A

(R1..R4)/4

(R1..R4)/4

(R1..R4)/4

(R1..R4)/4

(R5..R8)/4

ADCPPBxPSUM

N/A

R1

R1..R2

R1..R3

R1..R4

R5

R5..R6

R5..R7

R5..R8

ADCPPBxRESULT

N/A

R1

R2

R3

R4

R5

R6

R7

R8

Regards,

Luke

  • +1
    TI__Mastermind 31945 points

    Hi Luke,

    Luke Chen said:
    Does PPB load ADCPPBxPSUM into ADCPPBxSUM only when ADCPPBxPCOUNT is equal to ADCPPBxLIMIT?

    JC: In addition to COUNT=LIMIT, PSUM will also be loaded to SUM if external HW sync as described in the ADC SYNC table in the PPB Oversampling section of the TRM or if SWSYNC bit is written is written to in the CONFIG2 register.

    Luke Chen said:
    When will ADCPPBxPSUM be cleared and ready to accumulate new ADCPPBxRESULT?

    JC: After the end of the SOC conversion (tLAT) + 2 SYSCLK cycles, PSUM is overwritten by the result of the first count or will be the accumulated result after the first count

    Luke Chen said:
    I use the table below to represent the contents of each register after every ADC EOC. Are the contents of this table correct?

    JC: On the third row, results will only be averaged (shifted) if LIMIT is set to power of 2 and SHIFT field in ADCPPBxCONFIG2 register is written with the corresponding n shift value, otherwise rest of the rows look correct.

    Best regards,

    Joseph