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CCS/TMS570LS3137: flexray

Austin Hu49
Prodigy 70 points
Part Number: TMS570LS3137

Tool/software: Code Composer Studio

When I tried TMS570LS31x FlexRay Sample Code using Code Composer Studio v7, I have a puzzle about those value assigned to Fray_PST register as attached.

Why does the instruction to assign the value 0xFFFFFFFF turn out to make the register oberved all 0's ?  Did I miss something fundamental ?

  • 0
    TI__Guru**** 168357 points
    HI,

    >>Why does the instruction to assign the value 0xFFFFFFFF turn out to make the register oberved all 0's ? Did I miss something fundamental ?
    That depends on the register; there are some registers that are "write only", which means that any writes to them perform the intended function but any reads return zero. Other types of registers are cleared when "1" is written to them - that is quite common in Interrupt flag registers.

    I did a quick search but couldn't locate this specific register bank on SPNU499b, but I suspect it is RTIINTFLAG on section 13.3.27.

    Regards,
    Rafael
  • 0 in reply to desouza
    Prodigy 70 points

    Hi Rafael,

    Your are right. Thank you.  My question is related to 23.19.2.2.2 instead.

    Regards,

    Austin

  • 0
    Guru 92251 points

    Austin Hu49 said:
    Why does the instruction to assign the value 0xFFFFFFFF turn out to make the register oberved all 0's ?

    The Status Interrupt Register (SIR) is "special" in that writing a 1 clears the corresponding bit:

    That means writing 0xFFFFFFFF to the SIR clears all bits which are set at a time of the write, and the SIR will then read as all zeros until the next event which sets one of the bits.