MSP430-使用来自BUTTON_ISR的jmp进行组装

Question

I currently have this BUTTON_ISR set up to increment r9 ( which holds what mode the program is currently in ) and then if the mode is 0 or 1 it will jump to a loop that flashes the red led and if it is in mode 2 or 3 it will just go to an empty loop so the light doesn't flash. However, my button only works once so I can get to mode 1 but then after that when I press the button on my board, nothing happens. Anyone know why this code is breaking my button? I think it has something to do with jumping out of button isr instead of using reti but I am unsure how to fix this, thanks.

BUTTON_ISR:
    push    r15
    push    r14

    ; button code here

    inc r9

.Ldebounce:

    bit.b   #0x08, &P1IN
    jnz     .Ldebounce
    mov     #120, r15
    call    #delay_ms

    bic.b   #BIT3, &P1IFG
    pop     r14
    pop     r15

    cmp #0, r9
    jeq .Lloop

    cmp #1, r9
    jeq .Lloop

    cmp #2, r9
    jeq .Loff

    cmp #3, r9
    jeq .Loff

    mov #0, r9
    jmp .Lloop


    reti

Answer 1

Your decisions using the values of R9 are being performed within the interrupt handler and based upon the value in the R9 register you perform a jump to the labels .Lloop or .Loff . There is no way for these routines to return to the interrupt function that you have here and even more important your last jump is an unconditional jump leaving no way back to the RETI end of interrupt function.

You should have a short interrupt function that sets a mode value preferably in RAM and some main background code that polls this location to see what action is to be taken. Using the R9 register in the way that you have is going to fail if your interrupt function ever returns and the R9 register is used by any of your main code. This failure will be either that the value of the R9 register could be changed between interrupts so the incrementing sequence that you expect will not happen, or your main code will fail because the value in R9 is incremented at some random time in the middle of some calculation.