Editing Advanced eXtensible Interface (section)

=== Bursts ===
[[File:AXI_Bursts.svg|thumb|upright=1.5|Example of FIXED, INCR and WRAP bursts]]

AXI is a [[Burst mode (computing)|burst-based]] [[Communication protocol|protocol]],<ref>{{cite web |author1=Arm Holdings |title=AMBA AXI and ACE Protocol Specification |url=https://static.docs.arm.com/ihi0022/e/IHI0022E_amba_axi_and_ace_protocol_spec.pdf |website=developer.arm.com |access-date=5 July 2019 |page=22 |language=en |archive-date=5 July 2019 |archive-url=https://web.archive.org/web/20190705083043/https://static.docs.arm.com/ihi0022/e/IHI0022E_amba_axi_and_ace_protocol_spec.pdf |url-status=dead }}</ref> meaning that there may be multiple data transfers (or beats) for a single request. This makes it useful in the cases where it is necessary to transfer large amount of data from or to a specific pattern of addresses.
In AXI, bursts can be of three types, selected by the signals ARBURST (for reads) or AWBURST (for writes):<ref>{{cite web |author1=Arm Holdings |title=AMBA AXI and ACE Protocol Specification |url=https://static.docs.arm.com/ihi0022/e/IHI0022E_amba_axi_and_ace_protocol_spec.pdf |website=developer.arm.com |access-date=5 July 2019 |pages=45–47 |language=en |archive-date=5 July 2019 |archive-url=https://web.archive.org/web/20190705083043/https://static.docs.arm.com/ihi0022/e/IHI0022E_amba_axi_and_ace_protocol_spec.pdf |url-status=dead }}</ref>

* FIXED
* INCR
* WRAP

In FIXED bursts, each beat within the transfer has the same address. This is useful for repeated access at the same memory location, such as when reading or writing a [[FIFO (computing and electronics)|FIFO]].

<math>\mathit{Address} = \mathit{StartAddress}</math>

In INCR bursts, on the other hand, each beat has an address equal to the previous one plus the transfer size. This burst type is commonly used to read or write sequential memory areas.

<math>\mathit{Address}_i = \mathit{StartAddress} + \mathit{i} \cdot \mathit{TransferSize}</math>

WRAP bursts are similar to the INCR ones, as each transfer has an address equal to the previous one plus the transfer size. However, with WRAP bursts, if the address of the current beat reaches the "Higher Address boundary", it is reset to the "Wrap boundary":

<math>\mathit{Address}_i = \mathit{WrapBoundary} + (\mathit{StartAddress} + \mathit{i} \cdot \mathit{TransferSize})\ \mathrm{mod}\ (\mathit{BurstLength} \cdot \mathit{TransferSize})</math>

with

<math>\mathit{WrapBoundary} = \left\lfloor \frac{\mathit{StartAddress}}{\mathit{NumberBytes} \cdot \mathit{BurstLength}} \right\rfloor \cdot (\mathit{NumberBytes} \cdot \mathit{BurstLength})</math>