DSP56F807 - Mutual exclusion using IPL 0 masking | Freescale DSPs

Technical discussions about Freescale (Motorola) DSPs (including the DSP56000, DSP56300, DSP56600, 56800 DSPs).

Hi, I need a mutual exclusion mechanism that allows access to two global variables as an atomic unit. To prevent code within an ISR from accessing one of the variables during this short period, I would like to mask IPL 0 interrupts while I access the pair and then unmask IPL 0 interrupts again when done. I would also like to put this code into a function that automatically determines if masking is already in affect (SR bit $0200 is set) so that the IPL 0 mask in the SR can be restored to its original state. This would allow the function to be called from inside or outside ISRs without the user keeping track of IPL 0 masking. Is it possible to use a BFSET instruction to set the IPL 0 mask bit in the SR and then test whether this bit was actually changed? This would then allow me to restore the mask after my "critical section" of code. So far I have not been suscessful in my attempts to do this, so I am wondering if anyone has a mechanism like this working. I am using an up to date version of Metrowerks with the 56F807 DSP. Thanks, Aaron

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Discussion Groups | Freescale DSPs | DSP56F807 - Mutual exclusion using IPL 0 masking

DSP56F807 - Mutual exclusion using IPL 0 masking - Aaron Needles - Oct 29 23:05:00 2002