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AMBA3 AXI - Exclusive access - 04/16/2015

In document on AXI3:

"The exclusive access monitor records the address and ARID value of any exclusive read

operation. Then it monitors that location until either a write occurs to that location or

until another exclusive read with the same ARID value resets the monitor to a different

address."

I have an example.

I have 2 Master and 2 bit ID per master. (out of order data & out standing address support)

M0 have master number is 0.

M1 have master number is 1.

When M0 is selected by the Arbiter, then M0 issue exclusive read to S0 with start address is 16h0000.

And then M1 is selected by the Arbiter, then M1 issue exclusive read to S0 with start address is 16h0000.

In two cases above, 2 exclusive read with same address is 16h0000 but different ARID.

What will happen with the monitor in my example???

After that, I assume that M1 issue exclusive write before M0.

What will S0 response to M0 and M1???

Best regards,

** Cao Phi

Parents
  • Hello Yasuhiko Koumoto,

    M0 is selected, then M0 issue exclusive read to S0 with start address is 16h0000.

    And then M1 is selected, then M1 issue exclusive read to S0 with start address is 16h0048.

    Will monitor in the S0 hold both of them (M1 infomation and M0 infomatinon)???

    Best regards,

    ** Cao Phi

Reply
  • Hello Yasuhiko Koumoto,

    M0 is selected, then M0 issue exclusive read to S0 with start address is 16h0000.

    And then M1 is selected, then M1 issue exclusive read to S0 with start address is 16h0048.

    Will monitor in the S0 hold both of them (M1 infomation and M0 infomatinon)???

    Best regards,

    ** Cao Phi

Children
  • Hello Cao Phi,

    M0 is selected, then M0 issue exclusive read to S0 with start address is 16h0000.

    And then M1 is selected, then M1 issue exclusive read to S0 with start address is 16h0048.

    Will monitor in the S0 hold both of them (M1 infomation and M0 infomatinon)???


    This case will depend on the exclusive capability of the S0.

    If S0 can hold only one exclusive information, the M1 exclusive access will be ignored.

    If S0 can hold more than one exclusive information, both the M0 and the M1 information also will be held in the S0.

    Best regards,

    Yasuhiko Koumoto.

  • Hello Yasuhiko Koumoto,

    So, IF 2 exclusive read from M0 and M1 to S0 are same address then S0 must hold only M0 infomation (In case S0 can hold more than one exclusive information)

    What will S0 response to M0 and M1???

    Best regards,

    Yasuhiko Koumoto.

  • Hello Cai Phi,

    EXOKAY for M0 and OKAY for M1.

    Regarding the reads, these responses would be useless.

    It would be significant for writes (i.e. STREX), because whether success or fail of STREX depends on the response.

    Best regards,

    Yasuhiko Koumoto.


  • Thank you very much.

    yasuhikokoumoto wrote:

    Hello Cai Phi,

    EXOKAY for M0 and OKAY for M1.

    Regarding the reads, these responses would be useless.

    It would be significant for writes (i.e. STREX), because whether success or fail of STREX depends on the response.

    Best regards,

    Yasuhiko Koumoto.