Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs
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13.4.4.10.1. Example: One Initiator Always Takes Precedence
In this example, one particular initiator’s packets always take precedence.
Consider a system that includes three initiators, A, B, and C. In this system, we require that initiator A always takes precedence over initiator B at each arbitration node, and initiator B always takes precedence over initiator C. To implement this arbitration scheme, we configure all QoS generators in fixed mode, and assign appropriate values for read and write urgency, as shown in the following table.
Initiator | QoS Mode | P1 (Read Urgency) | P0 (Write Urgency) |
---|---|---|---|
A | Fixed (mode 0) | 0x3 | 0x3 |
B | Fixed (mode 0) | 0x2 | 0x2 |
C | Fixed (mode 0) | 0x1 | 0x1 |
In fixed mode, initiators by default have a read urgency of 1 and write urgency of 0. So initiator C has equal urgency for reads and higher urgency for writes compared to all the other initiators in the system.