Hi guys,

I have faced an interesting issue in programming the ARM 7 processor. Code was written in assembly to output a pattern on a keil ARM kit. the IDE used was uVision. anyways here is the code:
FIO_BASE_ADDR	EQU 	0x3FFFC000                ; Initializing addresses of registers 
FIO2DIR                     EQU 0x40    
FIO2MASK      	EQU 0x50
FIO2PIN   	            EQU 0x54  
FIO2SET                     EQU 0x58
FIO2CLR    	            EQU 0x5C

DELAY_COUNT		EQU 12000                  ; Initializing delay to one second 

;----------------------- Pin Connect Block Definitions ------------------------- 

PCB_BASE               EQU 0xE002C000      ; PCB Base Address
PINSEL0_OFS          EQU 0x00                   ; PINSEL0  Address Offset
PINSEL1_OFS          EQU 0x04                   ; PINSEL1  Address Offset
PINSEL2_OFS          EQU 0x08                   ; PINSEL2  Address Offset
PINSEL3_OFS          EQU 0x0C                  ; PINSEL3  Address Offset
PINSEL4_OFS          EQU 0x10                   ; PINSEL4  Address Offset
PINSEL5_OFS          EQU 0x14                   ; PINSEL5  Address Offset
PINSEL6_OFS          EQU 0x18                   ; PINSEL6  Address Offset
PINSEL7_OFS          EQU 0x1C                   ; PINSEL7  Address Offset
PINSEL8_OFS          EQU 0x20                   ; PINSEL8  Address Offset
PINSEL9_OFS          EQU 0x24                   ; PINSEL9  Address Offset
PINSEL10_OFS        EQU 0x28                   ; PINSEL10 Address Offset

						          ; End of initializing addresses of registers
                AREA    RESET, CODE, READONLY
          ; Main program
MOV		R0,#0x0				; R0 = Counter

     						          ;Initializing Port2
    	     MOV		R1, #0x0	      	        ;PINSEL10=0x0; ; Disabling the 
                 LDR		R2, =PCB_BASE   	        ; ETM interface
      	     STR		R1,[R2, PINSEL10_OFS]
The problem is at the line:

I have to insert 2 NOPs after it in order for the program to work, otherwise it will freeze and nothing is outputted on the LEDs.

I was thinking it might be a structural hazard in the pipeline, but couldn't figure out exactly why. the instruction after it is a MOV for R1.

Any ideas will be greatly appreciated.