• State Accepted Answer
  • Locked Locked
  • Replies 5 replies
  • Subscribers 349 subscribers
  • Views 17155 views
  • Users 0 members are here
Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

AXI3 & AXI4 wrap burst length

Utkarsh Jain

Hi,

Was going through AXI spec.

As per AXI spec:

"AXI3 supports burst lengths of 1 to 16 transfers, for all burst types."

"AXI4 extends burst length support for the INCR burst type to 1 to 256 transfers. Support for all other burst types in

AXI4 remains at 1 to 16 transfers."

Also, as per AXI spec:

"for wrapping bursts, the burst length must be 2, 4, 8, or 16"

These are two contradicting lines for WRAP burst type. Can anyone confirm what's allowed specifically for AXI3 & AXI4?

Thanks

Utkarsh

Parents
  • 0 in reply to Utkarsh Jain

    Hi,


    the below is from A3.4.1 Address structure of AMBA® AXI™ and ACE™ Protocol
    Specification AXI3™, AXI4™, and AXI4-Lite™ ACE and ACE-Lite™ ARM IHI 0022E (ID022613)".
    Please read the following descriptions and the questions would be solved.

    Burst length
    The burst length is specified by:
    • ARLEN[7:0], for read transfers
    • AWLEN[7:0], for write transfers.
    In this specification, AxLEN indicates ARLEN or AWLEN.
    AXI3 supports burst lengths of 1 to 16 transfers, for all burst types.
    AXI4 extends burst length support for the INCR burst type to 1 to 256 transfers. Support for all other burst types in
    AXI4 remains at 1 to 16 transfers.
    The burst length for AXI3 is defined as,
    Burst_Length = AxLEN[3:0] + 1
    The burst length for AXI4 is defined as,
    Burst_Length = AxLEN[7:0] + 1, to accommodate the extended burst length of the INCR burst type in AXI4.
    AXI has the following rules governing the use of bursts:
    • for wrapping bursts, the burst length must be 2, 4, 8, or 16
    • a burst must not cross a 4KB address boundary
    • early termination of bursts is not supported.
    No component can terminate a burst early. However, to reduce the number of data transfers in a write burst, the
    master can disable further writing by deasserting all the write strobes. In this case, the master must complete the
    remaining transfers in the burst. In a read burst, the master can discard read data, but it must complete all transfers
    in the burst.

    Best regards,
    Yasuhiko Koumoto.

Reply
  • 0 in reply to Utkarsh Jain

    Hi,


    the below is from A3.4.1 Address structure of AMBA® AXI™ and ACE™ Protocol
    Specification AXI3™, AXI4™, and AXI4-Lite™ ACE and ACE-Lite™ ARM IHI 0022E (ID022613)".
    Please read the following descriptions and the questions would be solved.

    Burst length
    The burst length is specified by:
    • ARLEN[7:0], for read transfers
    • AWLEN[7:0], for write transfers.
    In this specification, AxLEN indicates ARLEN or AWLEN.
    AXI3 supports burst lengths of 1 to 16 transfers, for all burst types.
    AXI4 extends burst length support for the INCR burst type to 1 to 256 transfers. Support for all other burst types in
    AXI4 remains at 1 to 16 transfers.
    The burst length for AXI3 is defined as,
    Burst_Length = AxLEN[3:0] + 1
    The burst length for AXI4 is defined as,
    Burst_Length = AxLEN[7:0] + 1, to accommodate the extended burst length of the INCR burst type in AXI4.
    AXI has the following rules governing the use of bursts:
    • for wrapping bursts, the burst length must be 2, 4, 8, or 16
    • a burst must not cross a 4KB address boundary
    • early termination of bursts is not supported.
    No component can terminate a burst early. However, to reduce the number of data transfers in a write burst, the
    master can disable further writing by deasserting all the write strobes. In this case, the master must complete the
    remaining transfers in the burst. In a read burst, the master can discard read data, but it must complete all transfers
    in the burst.

    Best regards,
    Yasuhiko Koumoto.

Children
No data