AXI Atomic Operation Filter

This module filters atomic operations (ATOPs), i.e., write transactions that have a non-zero aw_atop value, from its slv to its mst port. This module guarantees that:

1. aw_atop is always zero on the mst port;

2. write transactions with non-zero aw_atop on the slv port are handled in conformance with the AXI standard by replying to such write transactions with the proper B and R responses. The response code on atomic operations that reach this module is always SLVERR (implementation-specific, not defined in the AXI standard).

This module is intended to be placed between masters that may issue ATOPs and slaves that do not support ATOPs. That way, this module ensures that the AXI protocol remains in a defined state on systems with mixed ATOP capabilities.

Interface Note

The AXI standard specifies that there may be no ordering requirements between different atomic bursts (i.e., a burst started by an AW with ATOP other than 0) and none between atomic bursts and non-atomic bursts [E2.1.4]. That is, an atomic burst may never have the same ID as any other write or read burst that is ongoing at the same time.