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10-4
Debug
Rev. A
Copyright 1999-2001 by LSI Logic Corporation. All rights reserved.
The ARM9E-S debug model is extended within the ARM966E-S with the
addition of scan chain 15. This scan chain is used for debug access to
the CP15 register bank when BIST is implemented. It allows the system
state within the ARM966E-S to be configured while in the debug state,
for instance, to enable or disable the SRAM before performing a debug
load or store.
The rest of this chapter describes the hardware debug extensions.
10.2 About the Debug Interface
The ARM966E-S debug interface is based on IEEE Std. 1149.1-1990,
Standard Test Access Port and Boundary-Scan Architecture
. Refer to
this standard for an explanation of the terms used in this chapter and for
a description of the Test Access Port (TAP) controller states.
The ARM9E-S processor core contains hardware extensions for
advanced debugging features, which make it easier to develop the
hardware, application software, and operating systems.
The debug extensions allow you to force the core into the
debug state
.
In the debug state, the ARM9E-S processor and ARM966E-S memory
system are effectively stopped and isolated from the rest of the system
in
halt mode
. From this mode, you can examine the internal state of the
ARM9E-S processor, the ARM966E-S system, and the external state of
the AHB while all other system activity continues as normal. When debug
is complete, the ARM9E-S processor restores the core and system state,
and resumes program execution.
In addition, the ARM9E-S supports a real-time debug mode called
monitor mode
, where instead of generating a breakpoint or watchpoint,
an internal Instruction Abort or Data Abort is generated. When monitor
mode is used in conjunction with a debug monitor program that is
activated by the abort exception entry, you can debug the ARM966E-S
while allowing the execution of critical interrupt service routines. The
debug monitor program typically communicates with the debug host over
the ARM966E-S debug communication channel. Monitor mode debug is
described in Section 10.10, “Real-Time Debug,” page 10-20.