A simple arm program that allows LED lights to shine. what's the problem?

A simple arm program that allows LED lights to shine. what's the problem? -- Linux general technology-Linux programming and kernel information. The following is a detailed description. A simple arm program with LED lights shining

. Text
. Global _ start
_ Start:
LDR R0, = 0x56000010 @; GPBCON Set
Mov r1, #0x00015400 @; set all output
Str r1, [r0]

Ldr r0, = 0x56000014 @; GPBDAT
On:
Mov r1, #0x00000000 @; all led on
Str r1, [r0]
Bl dly @; delay

Off:
Mov r2, #0x000001e0 @; all led off
Str r2, [r0]
Bl dly
B on

Dly: @; delay 1000*1000 unit
Mov r3, #1000.
Dly0:
Mov r4, #1000.
Dly1:
Sub r4, r4, #1
Cmp r4, #0
Bne dly1
Sub r3, r3, #1
Cmp r3, #0
Bne dly0
Mov pc, lr @; return

Main_loop:
B main_loop

Let's take a look at the code.
After compilation, binfiles can be generated, but the running results in the memory are not as expected. all the lights are on, but they are not flashing. why?
Is there any problem with the code?
Remove the Latency. the on or off code is valid and can be switched on.