
MOTOROLA
6-22
EXCEPTIONS
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RCPU
REFERENCE MANUAL
When a machine check exception is taken, instruction execution resumes at offset
0x00200 from the physical base address indicated by MSR[IP].
6.11.2.2 Checkstop State
The processor enters the checkstop state when a machine check exception oc-
curs, MSR[ME] equals zero, and either debug mode is disabled or DER[CHSTPE]
is cleared. When the processor is in the checkstop state, instruction processing is
suspended and generally cannot be restarted without resetting the processor. The
contents of all latches (except any associated with the bus clock) are frozen within
two cycles upon entering checkstop state so that the state of the processor can be
analyzed.
6.11.2.3 Machine-Check Exceptions and Debug Mode
The processor enters debug mode when a machine check exception occurs, de-
bug mode is enabled, and either MSR[ME] = 0 and DER[CHSTPE] = 1, or
MSR[ME] = 1 and DER[MCIE] = 1. Refer to
SECTION 8 DEVELOPMENT SUP-
PORT
for more information.
6.11.3 External Interrupt (0x00500)
The interrupt controller in the on-chip peripheral control unit signals an external in-
terrupt by asserting the IRQ input to the processor. The interrupt may be caused
by the assertion of an external IRQ pin, by the periodic interrupt timer, or by an on-
chip peripheral. Refer to
System Interface Unit Reference Manual
(SIURM/AD) for
more information on the interrupt controller.
The interrupt may be delayed by other higher priority exceptions or if the MSR[EE]
Table 6-14 Register Settings Following a Machine Check Exception
Register
Setting Description
SRR0
Set to the effective address of the instruction that caused the interrupt.
SRR1
0
1
[2:15]
[16:31]
Cleared
Set for instruction-fetch related errors, cleared for load-store related errors
Cleared
Loaded from MSR[16:31].
MSR
IP
ME
LE
Other bits
No change
Cleared to zero
Set to value of ILE bit prior to the exception
Cleared
DSISR (L-bus case
only)
[15:16]
Set to bits [29:30] of the instruction if X-form
Set to 0b00 if D-form
Set to bit 25 of the instruction if X-form
Set to bit 5 of the instruction if D-form
Set to bits [6:15] of the instruction
17
[22:31]
DAR (L-bus case
only)
Set to the effective address of the data access that caused the exception.
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