.extern f

.text
my_string:
    .string "HELLO WORLD!\r\n\r\n"
    .quad 0x00
    .quad 0x5a

.align 4
.global _start
_start:
    /* does nothing special */
	mov r13, #0x8000

    mov r1, #16

1:
    ldr r0, =my_string
    bl printk
    sub r1, #1
    cmp r1, #0
    b 1b

lup:
    b lup


.global printk
printk:
    stmfd r13!, {r0, r1, r2, r3, r4, r14}

    /* disable UART interrupts */
    mov r2, #0x8004
    movt r2, #0x01c2

    ldr r1, [r2]
    and r1, #0xfffffffc
    str r1, [r2]

    /* mask interrupts in CPU */
    cpsid if

    /* TBR */
    mov r2, #0x8000
    movt r2, #0x01c2

1:
    ldr r1, [r0]
    add r0, #4

    mov r4, #4
2:
    and r3, r1, #0xff
    mov r1, r1, lsr#8
    cmp r3, #0
    beq 3f
    str r3, [r2]
    sub r4, #1
    cmp r4, #0
    bne 2b
    b 1b
3:

    ldmfd r13!, {r0, r1, r2, r3, r4, r15}