.global _start
_start:

ldr r7, =SW
ldr r1, =LED
ldr r2, =SSLED

ldr r3, [r7]
str r3, [r1]

mov r9, #0
mov r10, #0
mov r11, #0
mov r12, #0

_cv1:
cmp r3, #1000
bge _sub1000

_cv2:
cmp r3, #100
bge _sub100

_cv3:
cmp r3, #10
bge _sub10

_cv4:
cmp r3, #1
bge _sub1

_LED1:
mov r4, r9
bl _comparator
mov r6, r0
lsl r6, #8

_LED2:
mov r4, r10
bl _comparator
add r6, r0
lsl r6, #8

_LED3:
mov r4, r11
bl _comparator
add r6, r0
lsl r6, #8

_LED4:
mov r4, r12
bl _comparator
add r6, r0

str r6, [r2]
b _start

_sub1000:
sub r3, #1000
add r9, #1
b _cv1
_sub100:
sub r3, #100
add r10, #1
b _cv2
_sub10:
sub r3, #10
add r11, #1
b _cv3
_sub1:
sub r3, #1
add r12, #1
b _cv4

_comparator:
_c0:
cmp r4, #0
bne _c1
mov r0,#0x3F
bx lr
_c1:
cmp r4, #1
bne _c2
mov r0,#0x06
bx lr
_c2:
cmp r4, #2
bne _c3
mov r0,#0x5B
bx lr
_c3:
cmp r4, #3
bne _c4
mov r0,#0x4F
bx lr
_c4:
cmp r4, #4
bne _c5
mov r0,#0x66
bx lr
_c5:
cmp r4, #5
bne _c6
mov r0,#0x6D
bx lr
_c6:
cmp r4, #6
bne _c7
mov r0,#0x7D
bx lr
_c7:
cmp r4, #7
bne _c8
mov r0,#0x07
bx lr
_c8:
cmp r4, #8
bne _c9
mov r0,#0x7F
bx lr
_c9:
mov r0,#0x67
bx lr

.data
.equ SW, 0xff200040
.equ LED, 0xff200000
.equ SSLED, 0xff200020