$regfile = "xm32e5def.dat"
$hwstack = 64
$swstack = 64
$framesize = 64

Dim Mcs_text As String * 17 , Mcs(16) As Byte At Mcs_text Overlay

Dim First_array(16) , Second_array(16) As Byte , I As Byte

For I = 1 To 16
     First_array(i) = I
Next

Xteaencode First_array(1) , Mcs(1) , 16                     ''this returns the encoded First_Array

End

_Xtea_encode_repeat:
  rcall _xtea_processV1
  rcall _xtea_loadk

  rcall _xtea_loadv0   ; load V0
  rcall _xtea_add_res  ; add to result
  rcall _xtea_saveV0   ;save to V0    ; <---------  stores the final values back in the same array?

 ;.........

  rcall _xtea_processv0
  rcall _xtea_loadk

  rcall _xtea_loadv1 ; load V1!
  rcall _xtea_add_res  ; add result to V1
  rcall _xtea_saveV1       ; <---------  stores the final values back in the same array?

 ;.........

_xtea_savev0:
  std y+0,r16
  std y+1,r15
  std y+2,r14
  std y+3,r13
ret

_xtea_savev1:
  std y+4,r16
  std y+5,r15
  std y+6,r14
  std y+7,r13
ret
 

(...)
I = Memcopy(First_array(1) , Second_array(1), 16)
Xteaencode Second_array(1) , Mcs(1) , 16                     ''this returns the encoded First_Array
(...)