2.3.1. AXI3 and AXI4 protocol conversion

This section describes:

AXI4 to AXI3

AXI4 long bursts are split into multiple AXI3 bursts, up to a length of 16 beats as required. You can determine the number of output transactions by the formula shown in Figure 2.1:

Figure 2.1. Determining the number of output transactions

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When more than one transaction is output, then each one is 16 beats apart from the last, which might not be of the same length.

AXI3 to AXI4

The maximum possible AXI4 output burst length is 16 beats, unless the downsizing function is also configured.

If there is a requirement to prevent AXI3 transactions creating long bursts, then you can configure a burst limiter function. The burst limiter requires a programmer interface to enable selection of burst limiting or no burst limiting. See registers for the AXI Slave Interface Block (ASIB), AXI internal network Interface Block (IB), and AXI Master Interface Block (AMIB) in Chapter 3 Programmers Model.

Note

AXI4 does not support locked transactions, therefore you must only use exclusive atomic accesses to access an AXI4 slave from an AXI3 master.

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