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nRF54L AUX-AP access port description and usage

Tomas Vanek

Hi all,

In the PDF version of nRF54L PRELIMINARY DATASHEET v0.8, in chapter

9.1 Debug access port:

in table 65: Access port overview

is listed AUX access port of AHB-AP with AP ID 1.

Figure 160: Debug and trace overview

shows AUX-AP connected to VPR trough AMBIX0 block.

In table 66 in chapter 9.2 Access port protection:

Access port protection overview registers UICR.AUXAPROTECT, TAMPC.PROTECT.­AP[0].­DBGEN
are described as "These registers control the generation of the AHB-AP DBGEN signal,
which controls debug access to the VPR AHB-AP. This is used to provide debug capability for VPR."

But there is no other info where any VPR debugging resides in AUX-AP memory space.
Moreover I didn't find any readable address in AUX-AP.

FLPR/VPR RISC-V coprocessor DM (debug module) registers are exposed @ 0x4004C000 / 0x5004C000 of APP-AP (AP ID 0)  address space as described
in 8.26.1 Registers

What is AUX-AP for? Is possible to use it for RISC-V DM access?

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  • 0

    The debug diagram in trace and debug chapter in PS is not very accurate,  the AHB-AP (AP0) can also access the VPR registers. The VPR debug registers are memory mapped on APB00, so they can be accessed through either AP0 and AP1. However, the AUX-AP can access only APB00 space on AMBIX0, a shown below:

    The main reason to have AP0 and AP1 (AUX-AP) to debug CM33 and VPR simultaneously using the corresponding APs. So the primary usage for AUX-AP is to use with RISC-V DM access as pointed in the question.

  • 0 in reply to ketiljo

    Thanks for the reply.

    Could you please go into details about accessing RISC-V DM over AUX-AP?

    I would expect DM registers at RISC-V debug spec conforming addresses of AUX-AP. But there is no access from SWD DAP.

    Datasheet, page 751 reads:

    UICR.AUXAPROTECT,
    TAMPC.PROTECT.AP[0].DBGEN

    These registers control the generation of the AHB-AP DBGEN signal,
    which controls debug access to the VPR AHB-AP. This is used to
    provide debug capability for VPR.

    and

    UICR and TAMPC are combined to enable or disable the access port protection. The access port is normally
    protected, and is opened when the following conditions are met:
    1. UICR.APPROTECT must be Unprotected.
    2. The corresponding TAMPC.PROTECT register must be written by firmware. See TAMPC signal protector
    for details on the procedure.

    Does it mean that AUX-AP access cannot be enabled by a debugger only without running some code on nRF54L?

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  • 0 in reply to ketiljo

    Thanks for the reply.

    Could you please go into details about accessing RISC-V DM over AUX-AP?

    I would expect DM registers at RISC-V debug spec conforming addresses of AUX-AP. But there is no access from SWD DAP.

    Datasheet, page 751 reads:

    UICR.AUXAPROTECT,
    TAMPC.PROTECT.AP[0].DBGEN

    These registers control the generation of the AHB-AP DBGEN signal,
    which controls debug access to the VPR AHB-AP. This is used to
    provide debug capability for VPR.

    and

    UICR and TAMPC are combined to enable or disable the access port protection. The access port is normally
    protected, and is opened when the following conditions are met:
    1. UICR.APPROTECT must be Unprotected.
    2. The corresponding TAMPC.PROTECT register must be written by firmware. See TAMPC signal protector
    for details on the procedure.

    Does it mean that AUX-AP access cannot be enabled by a debugger only without running some code on nRF54L?

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