9.7.5 AXI protocol restrictions

The ACP is AXI compliant, but not does support the full protocol.

The following AXI protocol restrictions apply:

  • The APROT[1] input is ignored and the APROT[1] output is always LOW on the AXI master buses and the AXI peripheral bus.
  • Only swap-like accesses are accepted, that is, a locked read followed by a nonlocked write. AWLOCKSC is not forwarded from the ACP to any master ports on AWLOCKM0[1] or AWLOCKM1[1]. These ports are always LOW.
  • The ACP does not support exclusive accesses, and there is no exclusive monitor. If either master attempts an exclusive read, the ACP returns an OKAY response instead of an EXOKAY response. The master can treat this as an error condition, indicating that the exclusive access is not supported. ARM recommends that the master does not perform the write portion of this exclusive operation.
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