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Inside Macintosh: Memory /

Chapter 1 - Introduction to Memory Management / Memory Management Reference

Memory Management Routines

Setting and Restoring the A5 Register

Any code that runs asynchronously or as a callback routine and that accesses the calling application's A5 world must ensure that the A5 register correctly points to the boundary between the application parameters and the application global variables. To accomplish this, you can call the SetCurrentA5 function at the beginning of any asynchronous or callback code that isn't executed at interrupt time. If the code is executed at interrupt time, you must use the SetA5 function to set the value of the A5 register. (You determine this value at noninterrupt time by calling SetCurrentA5.) Then you must restore the A5 register to its previous value before the interrupt code returns.

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Subtopics

SetCurrentA5

SetA5