Arbiters

ROHD-HCL implements a generic abstract Arbiter class that other arbiters can extend. It accepts a List of requests, where each request is a 1-bit signal indicating that there is a request for a resource. The output grants is a List where each element corresponds to the request with the same index. The arbiter implementation decides how to select which request receives a grant.

Stateful Arbiter

A StatefulArbiter is an Arbiter which can hold state, and thus requires a clk and reset.

Priority Arbiter

The PriorityArbiter is a combinational (stateless) arbiter that always grants to the lowest-indexed request.

PriorityArbiter Schematic

Round Robin Arbiter

The RoundRobinArbiter is a StatefulArbiter which grants requests in a "fair" way so that all requestors get equal access to grants. There are two implementations available for RoundRobinArbiter:

• MaskRoundRobinArbiter is the default implementation if you create a RoundRobinArbiter. It uses internal request and grant masks to store state for fair arbitration.
• RotateRoundRobinArbiter is an alternative implementation which uses a PriorityArbiter and two rotators controlled by a last-granted state.