Quartus® Prime Pro Edition User Guide: Platform Designer

ID 683609
Date 4/17/2025
Public
Document Table of Contents

6.12.4.2. Data Width of Crossbar

As AXI Streaming Crossbar Parameters mentions, the following data widths are supported on ingress and egress interfaces: 8, 16, 32, 64, 128, 256. 

When data width mismatch occurs at system configuration time, a width adapter capable of doing wide-to-narrow and narrow-to-wide data width conversion is automatically inserted.

The data width of the multi-hop crossbar varies depending on the widths of transmitters and receivers connected to it. This leads to the following scenarios: 

All transmitters and receiver interfaces are of equal data width

The data width of the multi-hop crossbar is equal to the width of transmitters and subordinates.

All transmitter interfaces have equal data width, and all receiver interfaces have equal data width

The transmitter data width is not equal to the receiver data width. 

  1. If the receiver interfaces’ data width is greater than the transmitter interfaces’ data width, the crossbar data width is set to the transmitter interfaces’ data width. Down conversion occurs at ingress ports.
  2. If the receiver interfaces’ data width is less than the transmitter interfaces’ data width, the crossbar data width is set to the transmitter interfaces’ data width. Up conversion is occurs at ingress ports. Narrow to wide converters use empty to indicate valid data bytes.

Transmitter interfaces, receiver interfaces have different data widths

Data width of the crossbar is set to the maximum data width in the system. Narrow to wide data conversion occurs with empty indicating valid data bytes. You can perform conversion on both sides if needed.