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MOTOROLA
MC68330 USER'S MANUAL
5- 71
The stack contents are identified by the SSW. In addition to identifying the fault type
represented by the stack frame, the SSW contains the internal processor state
corresponding to the fault.
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TP
MV
0
TR
B1
B0
RR
RM
IN
RW
LG
SIZ
FUNC
TP
BERR frame type
MV
MOVEM in progress
TR
Trace pending
B1
Breakpoint channel 1 pending
B0
Breakpoint channel 0 pending
RR
Rerun write cycle after RTE
RM
Faulted cycle was read-modify-write
IN
Instruction/other
RW
Read/write of faulted bus cycle
LG
Original operand size was long word
SIZ
Remaining size of faulted bus cycle
FUNC
Function code of faulted bus cycle
The TP field defines the class of the faulted bus operation. Two BERR exception frame
types are defined. One is for faults on prefetch and operand accesses, and the other is for
faults during exception frame stacking:
0=Operand or prefetch bus fault
1=Exception processing bus fault
MV is set when the operand transfer portion of the MOVEM instruction is in progress at
the time of a bus fault. If a prefetch bus fault occurs while prefetching the MOVEM opcode
and extension word, both the MV and IN bits will be set.
0=MOVEM was not in progress when fault occurred
1=MOVEM in progress when fault occurred
TR indicates that a trace exception was pending when a bus error exception was
processed. The instruction that generated the trace will not be restarted upon return from
the exception handler. This includes MOVEM and released write bus errors indicated by
the assertion of either MV or RR in the SSW.
0=Trace not pending
1=Trace pending
B1 indicates that a breakpoint exception was pending on channel 1 (external breakpoint
source) when a bus error exception was processed. Pending breakpoint status is stacked,
regardless of the type of bus error exception.
0=Breakpoint not pending
1=Breakpoint pending
B0 indicates that a breakpoint exception was pending on channel 0 (internal breakpoint
source) when the bus error exception was processed. Pending breakpoint status is
stacked, regardless of the type of bus error exception.