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TMS570LC4357: IOMM: PINMMRx reserved fields default value

Part Number: TMS570LC4357

Hi,

I am setting up the IOMM PINMMR registers to setup our system, and until now I was initializing PINMMR registers with 32 bits writes, that initialize the 4 fields of each PINMMR register.

But then I noticed 2 things:

  • some parts of the PINMMR registers are not documented in Table 6-1 of TMS570LC4357 TRM chapter 6 (as instance PINMM4[24-31]):
  • some PINMMR are indicated as "reserved" in the same table: my code didn't initialize those registers since they are marked as reserved

Additionnally, when looking with a debugger to those memory mapped register, I can see that the default values are sometimes 0x1, sometimes 0x2 and some other times 0x0 (this value is not documented).

So my question is the following: Do those 2 specific types of sections (partial PINMMR undocumented and PINMMR locations marked as "reserved") carry any relevant information used internally by the TMS570 to work as intended, or not?

The answer will determine if the values on reset needs to be kept or even needs to be forced (in our design, the safety recommendation is to ensure a proper configuration by assuming that the default reset values of the CPU registers could be different from the documentation), or if any value can be written with no impact on the system.

If writing to those locations have no effect, where could I find the information in the documentation in order to justify my requirements at detailed design level?

Best regards,

Gael

  • Hello Gael,

    No, there is no flip-flop for those reserved fields. Writing to those reserved locations have no effect to the MCU performance. 

     

  • Hi QJ,

    Thanks for this information.
    Where can I find this piece of information in the documentation?
    Best regards,
    Gael
  • Hello Gael,

    The TRM documents that the PINMMR uses one-hot encoding scheme, and also states that If an un-implemented alternate function is selected, the default function will be used.
  • Hi QJ,

    Yes, I found that too, but those sentences apply to used fields of the PINMMR registers only, right?
    But for what you replied in your first reply, is there any information about it in the documentation?

    Best regards
    Gael
  • Hello Gael,

    It is also for the unimplemented fields or unused field of the PINMMR registers, for example bit[31:24] of PINMMR2. It is not for the unimplemented PINMMR registers for example PINMMR5/6/7.

    I am sorry I don't have the documentations related to the circuitry inside the IC.
  • Hi QJ,

    I guess you meant PINMMR4 instead of PINMMR2.

    For that specific field (bits 31-24) of PINMMR4, the sentence "If an un-implemented alternate function is selected, the default function will be used." seem applicable only to 8-bit fields of PINMMR registers where a physical pin is attached, am I right? And when a PINMMR register is completely reserved (PINMMR5/6/7), I guess also that is because none of its 8-bit field is attached to any physical pin, right?

    Is it possible to add this clarification in the documentation? This will provide confidence that a write to those locations don't affect the system.

    Best regards,

    Gael

  • Hello Gael,

    You are correct. The sentence of "If an un-implemented alternate function is selected, the default function will be used." is only applicable to 8-bit fields of PINMMR registers where a physical pin is attached. For PINMMR 5/6/7, none of its 8-bit field is attached to any physical pin.

    I will discuss this requirement with our TRM owner. Thanks