B6.6 Debug access to coprocessor registers usage constraints

The Cortex®‑M33 processor does not support a mechanism to read and write registers located in external coprocessors from a debugger.

Arm® recommends you implement a coprocessor with a dedicated AHB or APB slave interface for the system to access the registers. If the debug view of the coprocessor is located in the PPB region of the memory map, you can use this interface to connect to the EPPB interface of the Cortex‑M33 processor.

If Secure debug is disabled, you must ensure the Secure information in the coprocessors is protected and not accessible when using a Non-secure debugger.

If the debug slave interface to the coprocessor is connected to the processor C-AHB or S-AHB master interfaces or the EPPB interface, you can use the HNONSEC and PPROT[2] signals on the AHB and APB interfaces respectively. This is because the security level of the debug requests routed through the processor from the D-AHB interface are subject to the debug access and authentication checks. If the coprocessor state is memory-mapped, then software can also access the information using load and store instructions. If your implementation uses this functionality, you must ensure the appropriate barrier instructions are included to guarantee ordering between coprocessor instructions and load/store operations to the same state.

Non-ConfidentialPDF file icon PDF version100230_0004_00_en
Copyright © 2016–2018 Arm Limited or its affiliates. All rights reserved.