Diff: binasm.s

Revision:

2:a81c9bc37084

Parent:

0:13e4e935bed6

--- a/binasm.s	Thu Jan 27 06:42:17 2011 +0000
+++ b/binasm.s	Fri Jan 28 02:40:35 2011 +0000
@@ -1,50 +1,52 @@
+ AREA |.data|, DATA, READWRITE
+ EXPORT leds
+         
+;BIT MASKS FOR LED1...LED4
+
+LED1 EQU 0x040000 
+LED2 EQU 0x100000
+LED3 EQU 0x200000
+LED4 EQU 0x800000
+ALLLEDS EQU LED1 :OR: LED2 :OR: LED3 :OR: LED4
+
+leds DCD LED1, LED2, LED3, LED4
+    
+    ALIGN
+
  AREA    |.text|, CODE, READONLY
  EXPORT  binasm
 
+GPIO1BASE  EQU 0x2009C020; GPIO port 1 base address
+GPIOSETOFF EQU 0x18
+GPIOCLROFF EQU 0x1C
+
 binasm PROC
     PUSH {R4, LR}
     
-    MOV R1, #0
-    MOV R2, #0
-    MOV R3, #0
-
     ; Load GPIO Port 1 base address in register R1 
-    LDR     R1, =0x2009C020 ; 0x2009C020 = GPIO port 1 base address
-    LDR     R4, =leds
+    LDR     R1, =GPIO1BASE
+    LDR     R4, =(leds+12) ; point to the last element of array
 
     ;CLEAR LEDS
-    MOV.W   R2, #0xB40000
-    STR   R2, [R1,#0x1C]
+    MOV   R2, #ALLLEDS
+    STR   R2, [R1,#GPIOCLROFF]
     
-    ADD R3, R3, #12 ; COUNTER FOR LOOP
+    MOV R3, #4      ; COUNTER FOR LOOP
     ADD R0, R0, #1  ; INCREMENT PARAMETER BY 1
     
 loop
-    ; CLEAR THE CARRY FLAG
-    ADC R0, R0, #0
-
-    LDR.W   R2, [R4, R3]
-    LSRS R0, R0, #1  
+    LDR  R2, [R4], #-4 ; load value from the address in R4 and decrement it by 4
+    LSRS R0, R0, #1    ; shift R0 right and set carry to the shifted out bit
 
-    STRCC   R2, [R1,#0x1C]  ; if==0, clear LED bit
-    STRCS   R2, [R1,#0x18]  ; if==1, set LED bit    
+    STRCC   R2, [R1,#GPIOCLROFF]  ; if==0, clear LED bit
+    STRCS   R2, [R1,#GPIOSETOFF]  ; if==1, set LED bit    
 
-    CMP R3, #0
-    SUB R3, R3, #4
+    SUBS R3, R3, #1
     BNE loop
     
     POP {R4, PC}
     ENDP
-
- AREA |.data|, DATA, READWRITE
- EXPORT leds
-         
-;BIT MASK FOR LED1...LED4
-
-leds DCD 0x040000 
-     DCD 0x100000
-     DCD 0x200000
-     DCD 0x800000
     
     ALIGN
+
     END
\ No newline at end of file