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MCF5307 User’s Manual
Exception Processing Overview
If a ColdFire processor encounters any type of fault during the exception processing of
another fault, the processor immediately halts execution with the catastrophic fault-on-fault
condition. A reset is required to force the processor to exit this halted state.
Reset
Exception
Asserting the reset input signal (RSTI) causes a reset exception. Reset has the highest exception
priority; it provides for system initialization and recovery from catastrophic failure. When assertion of
RSTI is recognized, current processing is aborted and cannot be recovered. The reset exception
places the processor in supervisor mode by setting SR[S] and disables tracing by clearing SR[T].
This exception also clears SR[M] and sets the processor’s interrupt priority mask in the SR to the
highest level (level 7). Next, the VBR is initialized to 0x0000_0000. Conguration registers controlling
the operation of all processor-local memories (cache and RAM modules on the MCF5307) are
invalidated, disabling the memories.
Note: Other implementation-specic supervisor registers are also affected. Refer to each of the
modules in this manual for details on these registers.
After RSTI is negated, the processor waits 80 cycles before beginning the actual reset exception
process. During this time, certain events are sampled, including the assertion of the debug
breakpoint signal. If the processor is not halted, it initiates the reset exception by performing two
longword read bus cycles. The longword at address 0 is loaded into the stack pointer and the
longword at address 4 is loaded into the PC. After the initial instruction is fetched from memory,
program execution begins at the address in the PC. If an access error or address error occurs before
the rst instruction executes, the processor enters the fault-on-fault halted state.
Unsupported
Instruction
Exception
If the MCF5307 attempts to execute a valid instruction but the required optional hardware module is
not present in the OEP, a non-supported instruction exception is generated (vector 0x61). Control is
then passed to an exception handler that can then process the opcode as required by the system.
Table 2-21. MCF5307 Exceptions (Continued)
Exception
Description
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Freescale Semiconductor, Inc.
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