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TMS570LS3137: PMM4 Software Readback of Written Configuration.

user4777395
Intellectual 480 points
Part Number: TMS570LS3137

Please tell me about PMM4 Software Readback of Written Configuration.
· It is Periodic / On-Demand, but is it supposed to periodically check write to registers?
· What is assumed specifically for the control register?

  • 0
    TI__Guru**** 191296 points
    Hi,
    Let's pick one PMM register for illustration. If you go to the PMM module you will find the LOGIPDPWRCTRL0 register. This register configures the on-chip power domains in different power states. Let's say you want to keep all the power domains in Active State. If there is a transient fault, it may flip a bit in this register such that a power domain becomes turned OFF. If you periodically read back the register as a diagnostic mechanism then you know when the register has changed state (from Active to OFF) . Of course there are other mechanisms which can also detect when certain modules inside a power domain are no longer operational since the power domain was turned off.
  • 0 in reply to Charles Tsai
    Intellectual 480 points

    Thanks Charles
    In connection with the above question, please tell me the difference between the following two functions

    ・ PMM3 Periodic Software Readback of Static Configuration Registers
    ・PMM4 Software Readback of Written Configuration

    Is there a problem with the next usage?
    Register not changed after initialization: PMM3
    Register to be changed by software: PMM4

  • 0 in reply to user4777395
    TI__Guru**** 191296 points
    Hi,
    There is a difference between PMM3 and PMM4. You will find similar diagnostics for other modules. Let's use the LOGIPDPWRCTRL0 register for illustration again. Suppose you want to turn off a power domain. What you will do is to write a value to the LOGIPDPWRCTRL0 to turn off a power domain. Let's say you want to turn off PD5 and hence you write a 0xA to the LOGICPDON3 field of the LOGIPDPWRCTRL0 register. How will you know for sure if the write really happens and completes. What happen if there is some permanent faults or even transient faults on the address/control signals where the value 0xA was never properly written to LOGICPDON3 field? If this is the case the PD5 is never turned off. Perhaps the data you wrote never got written to the LOGIPDPWRCTRL0 register but instead some other registers due to address faults. Here you will do PMM4 as a diagnostic to read back what you just wrote to make sure the write was complete to the intended address.

    Sometime down the road what happens if there is a transient fault that flips a bit in the LOGICPDON3 resulting in the PD5 getting changed from OFF state to Active state again? If you implement PMM3 where you periodically read the LOGIPDPWRCTRL0 register you will come to know that a fault might have happened. Note that when a power domain is changed from OFF to Active you may not notice it. It will burn a little more power but your application will continue to run fine. Unless you implement PMM3, you will not know the power domain has been turn Active due to transient faults.