.global _start

.equ IODIR0, 0xE0028008
.equ IOCLR0, 0xE002800C
.equ IOSET0, 0xE0028004

.text
   b _start
   b undef_handler
   b SVC_handler
   b PAbt_handelr
   b DAbt_handler
   b RFU_handler
   b IRQ_handler
   b FIQ_handler
undef_handler:
SVC_handler:
PAbt_handelr:
DAbt_handler:
RFU_handler:
IRQ_handler:
FIQ_handler:
   b undef_handler /* do nothing */

delay:
   mov r0, #10 
dowaitloop:
   subs r0,#1
   bne dowaitloop
   bx lr 

_start:
MOV r3, #0xFFFFFFFF
LDR r4, =IODIR0
LDR r1, =IOCLR0
LDR r2, =IOSET0
str r3, [r4]
loop:

str r3, [r2]

bl delay

str r3, [r1]
bl delay
b loop