12.2.1 Early BRESP

According to the AXI3 specification, BRESP answers on response channels must be returned to the master only after the master sends the last data. Cortex®‑R8 processor cores can also deal with BRESP answers returned when the address is accepted by the slave, regardless of whether data is sent or not.

This enables the core to provide a higher bandwidth for writes if the slave can support the Early BRESP feature. Cortex‑R8 processor cores set the AWUSER[8] bit to indicate to the slave that it can accept an early BRESP answer for this access. This feature can optimize the performance of the core, but the Early BRESP feature generates non-AXI3 compliant requests. When a slave receives a write request with AWUSER[8] set, it can either give the BRESP answer after the last data is received, AXI3 compliant, or in advance, non-AXI3 compliant. The L2C-310 Cache Controller supports this non-AXI3 compliant feature.

This feature is enabled by default. The Cortex‑R8 processor core does not require any programming to enable this feature.

Note:

To support this optimization, you must program the L2C-310 Cache Controller. See the ARM® CoreLink™ Level 2 Cache Controller L2C-310 Technical Reference Manual.
Non-ConfidentialPDF file icon PDF versionARM 100400_0001_03_en
Copyright © 2015–2017 ARM Limited or its affiliates. All rights reserved.