9.7.6 ACP bridge

The ACP contains an optional ACP bridge. This bridge has an optional ECC support and has an impact on the performance.

With the ACP bridge:

  • The ACP is ECC protected if ECC is present on the bus.
  • All types of AXI transfer are supported.
  • There are no special timing recommendations between the AXI address channel and the AXI data channel.

Without the ACP bridge:

  • The ACP is not ECC protected.
  • Only the following accesses are supported:

    • For 32 bytes, AxLENSC = 0x3, AxSIZESC = 0x3, AxBURSTSC = 0b01 (incr), and AxADDRSC[4:0] = 0b00000.

    • For 32 bytes, AxLENSC = 0x3, AxSIZESC = 0x3, AxBURSTSC = 0b10 (wrap), and AxADDRSC[2:0] = 0b000.
    • For 16 bytes, AxLENSC[3:0] = 0x1, AxSIZESC[1:0] = 0x3, AxBURSTSC[1:0] = 0b01 (incr), and AxADDRSC[3:0] = 0b0000.
    • For 8 bytes: AxLENSC = 0x0, AxSIZESC = 0x3, AxBURSTSC = any, and AxADDRSC = any.

    The x in the signal name represents either R for read or W for write.

    All other access types generate a slave error.

  • A write access can be accepted every four cycles.
  • The addresses must be sent at least six cycles before the data to optimize performance on the ACP transfers.
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