Level Two Interface

9.4.6AXI slave characteristics

This section describes the capabilities of the AXI slave interface, and the attributes of its AXI port. You must not make any other assumptions about the behavior of the AXI slave port except that it conforms to the AMBA AXI Protocol Specification.

The AXI slave interface supports merging of data. When handling an AXI burst of data less than 64-bits wide, the AXI slave interface attempts to perform the minimum number of TCM accesses required to read or write the data. When an ECC error scheme is in use, this sometimes reduces the number of read-modify-write sequences that the AXI slave must perform.

The AXI slave interface does not support:

Security Extensions, all accesses are secure, so AxPROT[1] is not used

data and instruction transaction signaling, so AxPROT[2] is not used

memory type and cacheability, so AxCACHE is not used

atomic accesses. The AXI slave accepts locked transactions but makes no use of the locking information, that is, AxLOCK.

The AXI slave interface has no exclusive access monitor. If there are any exclusive accesses, the AXI slave interface responds with an OKAY response.

The width of the ID signals for the AXI slave port is 8 bits.

You must avoid building the processor into an AXI system that requires more than 8 bits of ID. The number of bits of ID required by a system can often be reduced by compressing the encoding to remove unused values. The AXI master port does not use all possible values. See Identifiers for AXI bus accesses on page 9-4for details.

Table 9-25shows the AXI slave port attributes.

 

 

Table 9-25 AXI slave interface attributes

 

 

 

Attribute

Value

Comments

 

 

 

Combined acceptance capability

7

-

 

 

 

Write interleave depth

1

All write data must be presented to the AXI slave interface in order

 

 

 

Read data reorder depth

1

The AXI slave interface returns all read data in order, even if the bursts

 

 

have different IDs

 

 

 

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ARM R4F, r1p3 manual AXI slave characteristics, AXI slave interface attributes