Intel® Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 10/04/2021
Public

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5.1.8.1.1. AXI Wide-to-Narrow Adaptation

For all cases of AXI wide-to-narrow adaptation, read data is re-packed to match the original size. Responses are merged, with the following error precedence: DECERR, SLVERR, OKAY, and EXOKAY.
Table 42.  AXI Wide-to-Narrow Adaptation (Downsizing)

Burst Type

Behavior

Incrementing

If the transaction size is less than or equal to the output width, the burst is unmodified. Otherwise, it is converted to an incrementing burst with a larger length and size equal to the output width.

If the resulting burst is unsuitable for the slave, the burst is converted to multiple sequential bursts of the largest allowable lengths. For example, for a 2:1 downsizing ratio, an INCR9 burst is converted into INCR16 + INCR2 bursts. This is true if the maximum burstcount a slave can accept is 16, which is the case for AMBA* 3 AXI slaves. Avalon® slaves have a maximum burstcount of 64.

Wrapping

If the transaction size is less than or equal to the output width, the burst is unmodified. Otherwise, it is converted to a wrapping burst with a larger length, with a size equal to the output width.

If the resulting burst is unsuitable for the slave, the burst is converted to multiple sequential bursts of the largest allowable lengths; respecting wrap boundaries. For example, for a 2:1 downsizing ratio, a WRAP16 burst is converted into two or three INCR bursts, depending on the address.

Fixed

If the transaction size is less than or equal to the output width, the burst is unmodified. Otherwise, it is converted into repeated sequential bursts over the same addresses. For example, for a 2:1 downsizing ratio, a FIXED single burst is converted into an INCR2 burst.