simuating assembly code in qemu

My code is as follows:

.text  
.global __start
__start:                     // Function "myadd" entry point.
     .fnstart
    mov r2,#0x200

   mov r1,#0x30
    str r1, [r2]       
    ldr r0, [r2]       
     bx lr           // Return by branching to the address in the link register.
     

when in run this code value is not written to the address 200

Thank You