I'm facing some strange behavior when implementing timer interrupts on the XMC1100 (XMC1100T016X0064)
Using DAVE, I selected a Manchester decoder on Slice 0, and a 1 millisecond timer on slice 1.
All seemed to work ok, until I started investigating some strange behaviour.
First I discovered that the interrupt priority was not behaving as expected.
The Manchester decoder interrupt was executing at lower priority than set. It was interrupted by an low priority interrupt which I found strange.
I checked every configuration register using the debugger and all seemed correct to me. (Slice 0 was set to 0, others to higher values (lower prio))
By pure luck I discovered that setting the priority for Slice 0 to Slice 1 solved the issue.
After digging deeper I found that Slice 0 triggers the interrupt handler/vector for slice 1 (CCU40_1_IRQHandler ; Handler name for SR CCU40_1)
and vice versa Slice 1 triggers interrupt for slice 0 (CCU40_0_IRQHandler ; Handler name for SR CCU40_0)
I was puzzled. How could my application ever have worked? I checked the Errata sheet but I was unable to find any information regarding this behaviour.
Then I discovered DAVE apparently knows about this because it "compensates" by generating the following macros:
#define MANCHESTERCoder_CCU4IRQHandler IRQ_Hdlr_22, which links the Manchester decoding library (Hardcoded to slice 0) to the interrupt handler of Slice 1
and
#define TIMER1_ISR IRQ_Hdlr_21, which links slice 0 interrupt to the slice 1 handler.
Questions:
- Is this a known issue?
- If it is, why isn't it in the Errata sheet?
- If it isn't why is DAVE compensating for this?
- Why are the interrupt priorities not switched for Slice 0 and 1 in the initialization code?
Using DAVE, I selected a Manchester decoder on Slice 0, and a 1 millisecond timer on slice 1.
All seemed to work ok, until I started investigating some strange behaviour.
First I discovered that the interrupt priority was not behaving as expected.
The Manchester decoder interrupt was executing at lower priority than set. It was interrupted by an low priority interrupt which I found strange.
I checked every configuration register using the debugger and all seemed correct to me. (Slice 0 was set to 0, others to higher values (lower prio))
By pure luck I discovered that setting the priority for Slice 0 to Slice 1 solved the issue.
After digging deeper I found that Slice 0 triggers the interrupt handler/vector for slice 1 (CCU40_1_IRQHandler ; Handler name for SR CCU40_1)
and vice versa Slice 1 triggers interrupt for slice 0 (CCU40_0_IRQHandler ; Handler name for SR CCU40_0)
I was puzzled. How could my application ever have worked? I checked the Errata sheet but I was unable to find any information regarding this behaviour.
Then I discovered DAVE apparently knows about this because it "compensates" by generating the following macros:
#define MANCHESTERCoder_CCU4IRQHandler IRQ_Hdlr_22, which links the Manchester decoding library (Hardcoded to slice 0) to the interrupt handler of Slice 1
and
#define TIMER1_ISR IRQ_Hdlr_21, which links slice 0 interrupt to the slice 1 handler.
Questions:
- Is this a known issue?
- If it is, why isn't it in the Errata sheet?
- If it isn't why is DAVE compensating for this?
- Why are the interrupt priorities not switched for Slice 0 and 1 in the initialization code?