Specifications

Table Of Contents
ARM Debugger 3 5 A R M S p e c i f i c I m p l e m e n t a t i o n s
©1989-2014 Lauterbach GmbH
TrustZone Technology
The Cortex-A and ARM1176 processor integrate ARM’s TrustZone technology, a hardware security
extension, to facilitate the development of secure applications.
It splits the computing environment into two isolated worlds. Most of the code runs in the ‘non-secure’ world,
whereas trusted code runs in the ‘secure’ world. There are core operations that allow you to switch between
the secure and non-secure world. For switching purposes, TrustZone introduces a new secure ‘monitor’
mode. Reset enters the secure world:
Only when the core is in the secure world, core and debugger can access the secure memory. There are
some CP15 registers accessible in secure state only, and there are banked CP15 registers, with both secure
and non-secure versions.
Debug Permission
Debugging is strictly controlled. It can be enabled or disabled by the SPIDEN (Secure Privileged Invasive
Debug Enable) input signal and SUIDEN (Secure User Invasive Debug Enable) bit in SDER (Secure Debug
Enable Register):
SPIDEN=0, SUIDEN=0: debug in non-secure world, only
SPIDEN=0, SUIDEN=1: debug in non-secure world and secure user mode
SPIDEN=1: debug in non-secure and secure world
SPIDEN is a chip internal signal and it’s level can normally not be changed. The SUIDEN bit can be
changed in secure privileged mode, only.
Debug mode can not be entered in a mode where debugging is not allowed. Breakpoints will not work there.
A Break command or a SYStem.Up will work the moment a mode is entered where debugging is allowed.
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Secure state