Chapter 5. Debug Support
5-39
Real-Time Debug Support
Execution continues at the instruction address in the vector corresponding to the breakpoint
triggered. All interrupts are ignored while the processor is in emulator mode. The debug
interrupt handler can use supervisor instructions to save the necessary context such as the
state of all program-visible registers into a reserved memory area.
When debug interrupt operations complete, the RTE instruction executes and the processor
exits emulator mode. After the debug interrupt handler completes execution, the external
development system can use BDM commands to read the reserved memory locations.
If a hardware breakpoint such as a PC trigger is left unmodified by the debug interrupt
service routine, another debug interrupt is generated after the completion of the RTE
instruction.
5.6.1.1 Emulator Mode
Emulator mode is used to facilitate non-intrusive emulator functionality. This mode can be
entered in three different ways:
•
Setting CSR[EMU] forces the processor into emulator mode. EMU is examined
only if RSTI is negated and the processor begins reset exception processing. It can
be set while the processor is halted before reset exception processing begins. See
Section 5.5.1, “CPU Halt.”
•
A debug interrupt always puts the processor in emulation mode when debug
interrupt exception processing begins.
•
Setting CSR[TRC] forces the processor into emulation mode when trace exception
processing begins.
While operating in emulation mode, the processor exhibits the following properties:
•
All interrupts are ignored, including level-7 interrupts.
•
If CSR[MAP] = 1, all caching of memory and the SRAM module are disabled. All
memory accesses are forced into a specially mapped address space signaled by
TT = 0x2, TM = 0x5 or 0x6. This includes stack frame writes and the vector fetch
for the exception that forced entry into this mode.
The RTE instruction exits emulation mode. The processor status output port provides a
unique encoding for emulator mode entry (0xD) and exit (0x7).
5.6.2 Concurrent BDM and Processor Operation
The debug module supports concurrent operation of both the processor and most BDM
commands. BDM commands may be executed while the processor is running, except those
following operations that access processor/memory registers:
•
Read/write address and data registers
•
Read/write control registers
For BDM commands that access memory, the debug module requests the processor’s local
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Страница 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Страница 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
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