hexdump.s

@ dumps memory. r1: address 
print_memory:
  push {r0-r6}
  ldr r6, =uart0
  ldr r6, [r6]

  mov r5, r1 @ store memory begin address

  mov  r1, #'\n'
  strb r1, [r6]

  mov r0, #0xff @ dump 256 bytes

print_memory_loop:
  ldrb r1, [r5]
  mov r2, r1
  and r1, r1, #0xf0 @ high nybble
  lsr r1, r1, #4
  add r1, r1, #'0'
  cmp r1, #'9'      @ greater than 9?
  addgt r1, r1, #8  @ then shift to A-F range
  strb r1, [r6]     @ output

  and r1, r2, #0x0f @ low nybble
  add r1, r1, #'0'
  cmp r1, #'9'      @ greater than 9?
  addgt r1, r1, #7  @ then shift to A-F range
  strb r1, [r6]     @ output

  mov  r1, #' '
  strb r1, [r6]

  add r5, r5, #1

  lsr r2, r0, #4
  lsl r2, r2, #4
  cmp r0, r2
  sub r0, r0, #1
  bne print_memory_loop

  mov  r1, #'\n'
  strb r1, [r6]

  cmp r0, #16
  bgt print_memory_loop

  pop {r0-r6}
  bx lr