Hi,
We are trying to implement Interrupt Nesting with the Timer_A interrupt.
As you know in case of Timer_A the TACCR1 CCIFG, TACCR2 CCIFG have a single interrupt vector TAIVAnd the manual says "if the TACCR1 and TACCR2 CCIFG flags are set simultaneously first the TACCR1 CCIFG is reset automaticallyAfter that TACCR2 CCIFG flag will generate another interrupt".
And regarding the Interrupt Nesting the manual mentions "Interrupt nesting is enabled if the GIE bit is set inside an interrupt service routine"
So in our program, we have enabled the Interrupt Nesting (with GIE bit set) inside the interrupt service routine of TACCR2 CCIFG & TACCR1 CCIFG so that the program accepts other interrupts also.(Timer is in continuous with compare mode)
Unfortunately the result in our case is, if the TACCR1 and TACCR2 CCIFG flags are set simultaneouslyTACCR1 CCIFG flag is processed but the TACCR2 CCIFG is ignored(canceled),but if we remove the Nesting(with GIE bit) then the TACCR2 CCIFG is also processed.
Please let us know if it is not possible to use Interrupt Nesting in case of TACCR1 CCIFG, TACCR2 CCIFG interrupts?
Regards.Paddu
Interrupt nesting for MSP430 is difficult to do and the benefits may be marginal. Usually there is nothing wrong in handling ISRs quickly and orderly one at a time. If you really want to juggle more than one ISRs, it is like a circus act and you might drop them if you are not skillful.
Yes, you should be able to handle nested TACCR1 CCIFG and TACCR2 CCIFG interrupts. But why do you want to?
Hello,
I just can join the post of old yellow cow (easier than old cow yellow).
If you want to do interrupt nesting you will lose the main loop (at least on MSP430) . Or in other words you will lose your programs flow.
Regards
Marco
Marco ... If you want to do interrupt nesting you will lose the main loop (at least on MSP430) . Or in other words you will lose your programs flow. ...
Why is that so? I can see that if you do not do it correctly you will lose the control of the CUP.
Thank you OCY,
Actually we would like to enable other interrupts also while processing TACCR1 CCIFG/TACCR2 CCIFG.
In case of TACCR0,TACCR1,TACCR2, the interrupt occurs when TACCR0=FFFFand then the TAIFG should occur as per the manual,but if we enable the Nesting (with GIE bit) the TAIFG seems to be ignored after processing TACCR0 CCIFG.
Below is the part our assembly code.
TA_HND: ADD &TAIV,PC ;Add offset to the jump table RETI JMP CCIFG_1_HND ; Vector 2: TACCR1 JMP CCIFG_2_HND ; Vector 4: TACCR2 RETI ; Vector 6: Reserve RETI ; Vector 8: Reserve JMP TAIFG_HND ; Vector 10: TAIFG RETI RETI
CCIFG_1_HND: ; Vector 2: TACCR1 Flag bis.w #GIE, SR ; Enable Nesting ．．． RETI
CCIFG_2_HND: ; Vector 4: TACCR2 Flag bis.w #GIE, SR ; Enable Nesting ．．． RETI
TAIFG_HND: ;Vector 10: TAIFG Flag bis.w #GIE, SR ;Enable Nesting ．．． RETI
RegardsPaddu
First a word of warning:
Interrupt nesting is only for very, very experienced coders. Your ISR needs to be either reentrant or teh code design mus tensure that the same interrupt cannot ever happen before the nesting ISR has finished. This is very difficutl and if not done properly and carefully , it will lead to unexplainable crashes that may even happen first when the product is already in the field.
If you want to handle all interrupts as fast as possible and want to spare the ISR exit and reentrance time, you can handle them in a loop:
while(1) switch(_even_in_range(TAIV,0x0e){ case 0: return; // no more interrupts pending, exit ISR here. case 2: break; // CCR1 interrupt case 4: break; // CCR2 interrupt case 6: case 8: case 0x0a: case 0x0c: break; // reseverd for CCR3..6 on larger TIemrA modules case 0x0a: break; // timer overflow }}
This will handle all pending interrupts in a loop until no more are pending, then exits the ISR
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Paddu,
The partial code you have shown are okay. But I do not know about the part that you did not show. I wrote a silly demo for the LaunchPad. You may want to take a look. 0508.Nest_ISR.txtI slow down the clocks and use the two LEDs on the board to show what is going on. The main loop turns on both LEDs dimly. The Timer is set up to generate 3 different interrupts almost at the same time every 5 seconds or so. The interrupt handlers blink the LED brightly in three different ways.This demo works as expected. If you turn on the nesting, it still works. The only difference is that the priorities are inverted and the stack is deeper. When interrupts are not nested, you see Green, Red, then Green+Red every 5 seconds or so. The stack is 10 bytes deep.When interrupts are nested, you see Green+Red, Red, then Green every 5 seconds or so. The stack is 22 bytes deep.
-- OCY
Thank you very much.