2.2. Arbitration scheme

In the HPM, you can configure each MI separately to have an arbitration scheme that is either:

The AW and AR channels have separate arbiters and can be programmed, if applicable, and interrogated separately through the APB programming interface, but both AW and AR channels are configured identically. Because the AW and AR channels are arbitrated separately, an MI can permit simultaneous read and write transactions from different SIs.

The arbitration mechanism registers the arbitration decision for use in the subsequent cycle. An arbitration decision taken in the current cycle does not affect the current cycle.

If no SIs are active, the arbiter adopts default arbitration, that is, the highest priority SI. If this occurs and then the highest priority interface becomes active in the same cycle as, or before any other SI, then this does not constitute a grant to an active SI and the arbitration scheme does not change its state.

If a QoS provision is enabled and active, only a subset of SIs is permitted to win arbitration, and it cannot be guaranteed that the default arbitration is among these. In these circumstances, no transaction is permitted to use the default arbitration, and arbitration must occur when there is an active SI.

Copyright © 2006-2007 ARM Limited. All rights reserved.ARM DDI 0422B