Arbitration Modes
The AXI4-Stream Switch core includes arbiter engines that grant the request to an AXI master when more than one AXI master issues a request. The AXI4-Stream Switch supports two types of arbitration modes. In all modes, the tlast signal needs to be deasserted for the arbiter to proceed to next state.
Fixed Priority
In this mode, the arbiter always prioritizes the most significant bit (MSB) ports as indicated by the bits shown in bold in the following example. Lower priority ports suffer from starvation.
| Request | 11100000 | 11100000 | 11100000 | 1110010 | 00001011 | 00000000 | 00001111 | 11111111 |
| Grant | 10000000 | 10000000 | 10000000 | 10000000 | 00001000 | 00000000 | 00001000 | 10000000 |
Round Robin 1
The arbitration starts from the MSB port. When more than two transaction requests are issued at the same time, the arbiter grants the request to the port sitting on the right-hand side nearest to the previously served port.
Example:
| Request | 11100000 | 11100000 | 11100000 | 1110010 | 00001011 | 00000000 | 00001111 | 11111111 |
| Grant | 10000000 | 01000000 | 00100000 | 00000010 | 00000001 | 00000000 | 00001000 | 00000100 |