J-Link ARMv8-M

This article describes the debugging specifics for devices based on the ARMv8-M architecture.

TrustZone

Secure debug access

In secure mode, access to all system resources (memory, peripherals, ...) is allowed. In this mode, the non-secure part as well as the secure part can be debugged. Latter one can be debugged in this mode, only.

Non-secure debug access

In non-secure mode, access to certain system resources (memory, peripherals, ...) is limited to protect resources which are classified as secure. If the DHCSR.S_SDE bit is cleared, secure invasive debug (switching from non-secure to secure domain) is prohibited. The following list gives an overview of restrictions which need to be considered in non-secure mode:

• The reset functionality (via SYSRESETREQ) can be disabled for non-secure mode using the AIRCR.SYSRESETREQS bit. Unfortunately, the debugger cannot read the SYSRESETREQS bit in non-secure mode thus cannot determine if reset functionality is available or not. The only possibility to determine if it's available or not is to issue a reset via AIRCR.SYSRESETREQ and to check if DHCSR.S_RESET_ST gets set afterwards. If not, reset is not available in the current configuration.