
MOTOROLA
Chapter 5. Exceptions
5-39
Exception Definitions
Section 2.1.2.14, “Instruction Address Breakpoint Registers (IABR and IABR2),” and
Chapter 11, “Debug Features,” provide more information about the instruction breakpoint
facility.
5.5.17 System Management Interrupt (0x01400)
The system management interrupt behaves like an external interrupt except for the signal
asserted and the vector taken. A system management interrupt is signaled to the G2 core by
the assertion of the core_smi signal. The interrupt may not be recognized if a higher priority
exception occurs simultaneously or if MSR[EE] is cleared when core_smi is asserted. Note
that core_smi takes priority over core_int if they are recognized simultaneously.
After the core_smi is detected (and provided that MSR[EE] is set), the G2 core generates a
recoverable halt to instruction completion. The G2 core requires the next instruction in
program order to complete or except, block completion of any following instructions, and
allow the completed store queue to drain (see Section 7.1, “Terminology and Conventions,”
for the definition). If any higher priority exceptions are encountered in this process, they
are taken first and the system management interrupt is delayed until a recoverable halt is
achieved. At this time the G2 core saves state information and takes the system
management interrupt.
The register settings for the external interrupt exception are shown in Table 5-23.
Table 5-22. Breakpoint Action for Multiple Modes Enabled for the Same Address
IABR[IE]
MSR[BE]
MSR[SE]
First Action
Next Action
Comments
1
1
0
Instruction
address
breakpoint
Trace (branch) Enabling both modes is useful only if both
trace and address breakpoint interrupts are
needed.
1
0
1
Instruction
address
breakpoint
Trace
(single-step)
Enabling both modes is useful only if different
breakpoint actions are required.
0
1
1
Trace (branch) None
The action for branch trace and single-step
trace is the same. Enabling both trace modes
is redundant except for hard stop on
branches.
1
1
1
Instruction
address
breakpoint
Trace
Enabling all modes is redundant. This entry is
for clarification only.
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