; p2_8.s
; Assembly program to toggle the LED0
;
            EXPORT  __Vectors
            EXPORT  Reset_Handler
            AREA    vectors, CODE, READONLY

__Vectors   DCD     0x20008000          ; Top of Stack
            DCD     Reset_Handler       ; Reset Handler

PORTBDIR    equ 0x41004480
PORTBOUTCLR equ 0x41004484
PORTBOUTSET equ 0x41004488

            AREA    PROG, CODE, READONLY
Reset_Handler
            ldr     r4, =0x40000000     ; make PB30 output
            ldr     r5, =PORTBDIR
            str     r4, [r5]
L1          ldr     r5, =PORTBOUTCLR    ; clear PB30 to turn on LED0
            str     r4, [r5]
            ldr     r0, =500            ; delay 500 ms
            bl      delay
            ldr     r5, =PORTBOUTSET    ; set PB30 to turn off LED0
            str     r4, [r5]
            ldr     r0, =500            ; delay 500 ms
            bl      delay
            b       L1                  ; loop forever

; delay milliseconds in R0
delay       ldr     r1, =332
DL1         subs    r1, r1, #1
            bne     DL1
            subs    r0, r0, #1
            bne     delay
            bx      lr
            end