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XIO2001: is BE function in active low?

Marvin Cantos
Expert 4455 points
Part Number: XIO2001

Hi Team, 

Good day, I am posting this inquiry on behalf of the customer.

For  Pins 'C/BE[0]' , 'C/BE[1]' , 'C/BE[2]' , 'C/BE[3]' we need to know if the BE function is active low also? or the 'C' only is the active low? And for 'C' function it will have the same number like 'BE' to be C0/BE0 and so on........?

Please help to advise. Thank you for extending your support.

Kind regards, 

Marvin

  • 0
    Guru 265220 points

    During the address phase, these pins specify the command (C = command, 4 bits = 16 possible values, such as read/write/configuration/memory/I/O).
    During the data transfer, these pins specify the size of the data (BE = byte enable, 4 bytes in one 32-bit word).

    All this is prescribed by the PCI specification.

  • 0 in reply to Clemens Ladisch
    TI__Expert 4455 points

    Hi Clemens, 

    Thank you for your prompt response. Please see the feedback from the customer.

    "So please provide pin names it will be  like c0/be0 and so on

    Also both c and cn be activelow"
     

    Please help to advise. Thank you for extending your support.

    Kind regards, 

    Marvin

  • 0 in reply to Marvin Cantos
    Guru 265220 points

    The four C bits specify the command. See section 3.1.1 of the PCI specification for the bit patterns; it is not possible to say they are active high or low.

    The BE bits are byte enables for the four bytes in the word; BE0 for the lowest byte, etc. They are active low.

    These bits are driven by the bus master. See the PCI specification for details.

  • 0 in reply to Clemens Ladisch
    TI__Expert 4455 points

    Hi Clemens, 

    Thank you for your response. Please see the feedback from the customer.

    "so the bar sign above C is wrong, it should be only above BE

    also for C pBins it have 4 and be C0, C1,C2, C3 along with BE0,BE1,BE2,BE3"

    Please help to advise. Thank you for extending your support.

    Kind regards, 

    Marvin

  • 0 in reply to Marvin Cantos
    Guru 265220 points

    The C pins are not booleans; it does not matter whether there is a bar or not.

    The C pins form a group; they are always regarded as a single 4-bit unit, never independently. Strictly speaking, they do not have numbers. But if you wanted, you could assign the same 0…3 numbers to them.