
MOTOROLA
Chapter 5. Exceptions
5-35
Exception Definitions
exception on
isync
instructions (when MSR[SE] is set); the G2 core does not take
the trace exception on
isync
instructions. Single-step instruction trace mode is
described in Section 5.5.12.1, “Single-Step Instruction Trace Mode.”
When MSR[BE] is set, the branch trace exception is taken after each branch
instruction is completed.
The G2 core deviates from the architecture by not taking trace exceptions on
isync
instructions. Single-step instruction trace mode is described in Section 5.5.12.2,
“Branch Trace Mode.”
Successful completion implies that the instruction caused no other exceptions. A trace
exception is never taken for an
sc
or trap instruction that takes a trap exception.
MSR[SE] and MSR[BE] are cleared when the trace exception is taken. In the normal use
of this function, MSR[SE] and MSR[BE] are restored when the exception handler returns
to the interrupted program using an
rfi
instruction.
Register settings for the trace mode are described in Table 5-19.
Note that a trace or instruction address breakpoint exception condition generates a soft stop
instead of an exception if soft stop has been enabled by the JTAG/COP logic. If trace and
breakpoint conditions occur simultaneously, the breakpoint conditions receive higher
priority.
When a trace exception is taken, instruction execution for the handler begins at offset
0x00D00 from the base address indicated by MSR[IP].
5.5.12.1 Single-Step Instruction Trace Mode
The single-step instruction trace mode is enabled by setting MSR[SE]. Encountering the
single-step breakpoint causes the following action—trap to address vector 0x00D00.
The single-step trace action traps after an instruction execution and completion.
Table 5-19. Trace Exception—Register Settings
Register
Setting Description
SRR0
Set to the address of the instruction following the one for which the trace exception was generated.
SRR1
0–15
16–31 Loaded from MSR[16–31]
Cleared
MSR
POW 0
TGPR 0
ILE
EE
PR
—
0
0
FP
ME
FE0
SE
BE
0
—
0
0
0
FE1
CE
IP
IR
DR
0
—
—
0
0
RI
LE
0
Set to value of ILE
F
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