56303 | 563xx | 5680 | 56805 | 5680x | 56F80 | 56F800DEMO | 56F805 | 56f807 | 56F830 | ADC | Bootloader | Codec | CodeWarrior | CW5 | CW6 | Debugger | DSP56303 | DSP56303EVM | DSP563xx | DSP5680 | DSP56800 | DSP56807 | DSP56858 | DSP56858EVM | DSP56F803 | DSP56F805 | DSP56F807 | DSP56F80x | DSP56F826 | DSP56F827 | DSP56F8xx | EVM | FFT | Flash_over_jtag | GPIO | Interrupt | Interrupts | JTAG | LCD | Linker | MCF5307 | Metrowerks | Modulus | MSCAN | PCMaster | PWM | Quad | Rif | RTOS | SDK | SPI

I'm running a round robin multitasker on a 56F801. Interrupts are heavily used, but not for task switching. When I go to change the stack pointer (SP) I find that I must lock out interrupts around the following: move x:(r3),sp nop move x:(sp)-,r1 move x:(sp)-,r2 move x:(r1)+,b rts where r3 contains the address of a different task's saved stack pointer. r1, r2, and b need to be preserved across task switching (r1 is used as a data stack pointer, r2 must be preserved, and b is the top element of the data stack that r1 points to) Adding a bfset #$200,sr and replacing the rts with an rti (to allow the pulling of the stacked status, therefore restoring the state of the interrupt mask) fixes this. eg: bfset #$200,sr move x:(r3),sp nop move x:(sp)-,r1 move x:(sp)-,r2 move x:(r1)+,b rti Also running the code with interrupts enabled but not occuring also fixes the problem. Only if I change sp with interrupts allowed and occuring does this code fail. I am assuming that the other 3 move instructions are not the problem though. I expect this is a problem with the chip's pipelining. I have not been able to find anything on-line, in the manuals, in the on-line ap notes or errata, or in this group. Any thoughts? What am I missing? Gary

(You need to be a member of motoroladsp -- send a blank email to motoroladsp-subscribe@yahoogroups.com )