MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
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Freescale Semiconductor
that both of these stores will be executed. ISR2 thereby thinks that it can access the data block coherently,
but the data block has been corrupted.
OSEK uses the GetResource and ReleaseResource system services to manage access to a shared resource.
To prevent this corruption of a coherent data block, modifications to PRI in INTC_CPR can be made by
those system services with the following code sequences. Processor recognition of interrupts must be
enabled before executing the GetResource code sequence.
GetResource:
raise PRI
mbar
isync
ReleaseResource:
mbar
lower PRI
10.5.5.2.2
Raised Priority Preserved
Before the instruction after the GetResource system service executes, all pending transactions have
completed. These pending transactions can include an ISR for a peripheral or software settable interrupt
request whose priority was equal to or lower than the raised priority. Also, during the epilog of the interrupt
exception handler for this preempting ISR, the raised priority has been restored from the LIFO to PRI in
INTC_CPR. The shared coherent data block now can be accessed coherently.
shows the
timing diagram for this scenario, and
explains the events. The example is for software vector
mode, but except for the method of retrieving the vector and acknowledging the interrupt request to the
processor, hardware vector mode is identical.
Summary of Contents for MPC5553
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