All Read and Write Management Requests are 64 bits wide. The only exception occurs for insert and update operations of the entry. The insert and update operations write whole entries. Size of a management request is always a multiple of 64 bits. For example, if the entry width is 512 bits then the insert or update operation uses a 512-bit wide management request.
AXI4-Lite supports configurable widths: a minimal 13-bit address/32-bit data mode and extended modes with 64-bit data and wider addresses to avoid address-indirection overhead. In minimal mode, each 64-bit management request from the driver is split into multiple AXI4-Lite operations. In wider modes (64-bit data with extended addressing), the same requests need fewer transactions, improving management performance.
The AXI4-Lite writes are assembled by the AXI4-Lite interface logic into single management requests regardless of the interface width configuration. The AXI4-Lite interface is a standard type. Refer to AXI4-Lite IPIF LogiCORE IP Product Guide (PG155).
- All outstanding write responses must be received before issuing a read.
- All outstanding read responses must be received before issuing a write.
The following table shows an example calculation for 100 Gb Ethernet rate. Keep in mind the calculated update rate only refers to the hardware resources, the final update rate is most likely limited by the table management software.
| Management Request Size [bits] | AXI4-Lite Write Operations [min / max] | Management Update rate [M updates/s] |
|---|---|---|
| 64 | 1 / 3 | 4.8 |
| 128 | 2 / 5 | 4.8 |
| 256 | 4 / 9 | 4.8 |
| 512 | 8 / 17 | 4.8 |
| 1024 | 16 / 33 | 4.8 |
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