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PCIe - SUBSYS_VNDR_ID register

one and zero
Mastermind 18136 points

Hi Champs,

in the PCIe Users Guide the Register SUBSYS_VNDR_ID is marked as read only.

But in the bitfield description Table 3-127 it is stated: PCIe Subsystem Vendor ID. Writable from internal bus interface. and PCIe Subsystem ID. Writable from internal bus interface.

What is true?

Kind regards,

one and zero

  • 0
    TI__Genius 12065 points

    One and zero,

    If it states as "Writable from internal bus interface" in the description of some of the "read-only" bits in PCIe registers (such as SUBSYS_VNDR_ID Register), it means those bits  are still writable by the local device itself.

    Those bits are supposed to be "read-only" by the host system software over the PCIe link. And the application software in the local device itself could initialize the values of these "read-only" bits to make them ready before the first accessing by the external host.

    The "read-only" bits without the statement of "writable from internal bus interface" in the description, should be truly "read-only" by both local device and external device/host.

    Hope it helps.

    Sincerely,

    Steven