6.2.6. Exclusive access checks

Table 6.8 lists the exclusive access checks performed by the protocol checker:

Table 6.8. Exclusive access checks

Bus type(s)Description of checkAMBA3 APB Protocol SpecificationAMBA3 AHB-Lite Protocol SpecificationAMBA4 AXI and ACE Protocol Specification
APB, AXI4-LiteA transaction cannot be exclusive or locked.Section 4.1 “AMBA 3 APB signals”-Section B1.1.1 “AXI4 signals not supported in AXI4-Lite”.
AHBA transaction cannot be exclusive.-Section 2.2 “Master signals”-
AXI3A transaction cannot be exclusive and locked.--Section A7.4 “Atomic access signaling”.
AXI3Recommended that locked transactions are only used to support legacy devices.--Section A7.4.1 “Legacy considerations”.
AXI4, ACE-LiteLocked accesses are not supported.--Section A7.3 “Locked accesses”.
AXI3, AXI4, ACE-LiteThe maximum number of bytes that can be transferred in an exclusive burst is 128.--Section A7.2.4 “Exclusive access restrictions”.
AXI3, AXI4, ACE-LiteThe number of bytes transferred in an exclusive access burst must be a power of 2.--Section A7.2.4 “Exclusive access restrictions”.
AXI4The burst length for an exclusive access must not exceed 16 transfers.--Section A7.2.4 “Exclusive access restrictions”.
AXI3, AXI4, ACE-LiteThe address of an exclusive transaction is aligned to the total number of bytes in the transaction.--Section A7.2.4 “Exclusive access restrictions”.
AXI3, AXI4, ACE-LiteRecommended that every exclusive write has an earlier outstanding exclusive read with the same ID.--Section A7.2.4 “Exclusive access restrictions”.
AXI3, AXI4, ACE-LiteRecommended that the address, size and length of an exclusive write with a given ID is the same as the address, size and length of the preceding exclusive read with the same ID.--Section A7.2.4 “Exclusive access restrictions”.

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