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MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
10-44
Freescale Semiconductor
• In Section 10.5.10 “Examining LIFO Contents”:
Removed: “Normally the user does not need to know the contents of the LIFO. One may not even know how deeply the LIFO
is nested. However, if one should want to read the contents, such as in debug mode, they are not memory mapped. The
contents still can be read by popping the LIFO and reading the PRI field in the INTC current priority register (INTC_CPR). The
code sequence is:
pop_lifo:
store to INTC_EOIR
load INTC_CPR, examine PRI, and store onto stack
if PRI is not zero or value when interrupts were enabled, branch to pop_lifo
When the examination is complete, the LIFO can be restored using this code sequence:
push_lifo:
load stacked PRI value and store to INTC_CPR
load INTC_IACKR
if stacked PRI values are not depleted, branch to push_lifo
Added: “Normally the user does not need to know the contents of the LIFO, or even how deep the LIFO is nested. Although
the LIFO contents are not memory mapped, the user can read the contents by popping the LIFO and reading the PRI field in
the INTC current priority register (INTC_CPR). Disabling processor recognition of interrupts while examining the LIFO
contents provides a coherent view of the preempted priorities. The code sequence is:
pop_lifo:
store to INTC_EOIR
load INTC_CPR, examine PRI, and store onto stack
if PRI is not zero or value when interrupts were enabled, branch to pop_lifo
When the user is finished examining the LIFO contents, it can be restored in software vector mode using the following code
sequence. In hardware vector mode, reading the INTC_IACKR does not push the INTC_CPR[PRI] onto the LIFO, therefore
the LIFO contents cannot be restored in hardware vector mode.
push_lifo:
load stacked PRI value and store to INTC_CPR
load INTC_IACKR
if stacked PRI values are not depleted, branch to push_lifo
NOTE
• Reading the INTC_IACKR acknowledges the interrupt request to the processor and updates the INTC_CPR[PRI] with the
priority of the preempting interrupt request. If the processor recognition of interrupts is disabled during the LIFO restoration,
interrupt requests to the processor can go undetected. However, because the peripheral or software settable interrupt
requests are not cleared, the peripheral interrupt request to the processor re-asserts when INTC_CPR[PRI] is lower than
the priorities of those peripheral or software settable interrupt requests.
Table 10-12. Changes to MPC5553/5554 RM for Rev. 4.0 Release (Continued)
Содержание MPC5553
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