Diff: my_leds.s

Revision:

2:968db132481b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/my_leds.s	Sat Jan 04 12:34:04 2020 +0000
@@ -0,0 +1,38 @@
+   AREA asm_demo, CODE, READONLY
+   EXPORT my_leds
+my_leds
+   PUSH    {R1, R2, R3, R4, LR}
+   LDR R1, =0x2009C020 ; loading the base.
+   AND R4, R0, #8 ;take biggest bit
+   AND R3, R3, #0 
+   ORR R3, R3, R4 ;put in R3
+   LSL R3, R3, #1 ;shift for spacing for pins
+   AND R4, R0, #6 ;take middle bits
+   ORR R3, R3, R4 ;put in R3
+   LSL R3, R3, #1 ;shift for spacing for pins
+   AND R4, R0, #1 ;take first bit
+   ORR R3, R3, R4 ;put in R3
+   LSL R3, R3, #18 ;shift to pin location in hex
+   STR R3, [R1, #0x18] ;turns on led with FIOSet
+   
+   BL      wait ; Call to wait
+   STR R3, [R1, #0x1C] ;clears LED with FIOClear
+   POP     {R1, R2, R3, R4, LR}
+   BX      LR
+   ALIGN   ; End of my_leds function
+   
+wait
+   PUSH    {R1, R2}
+   MOV.W R1, #1
+   LDR R2, =5000000
+           ; Omitted loop code goes here
+loop_entry
+        CMP R1, R2
+        BGT loop_exit
+        ADD R1,R1, #1
+        B loop_entry
+loop_exit
+   POP     {R1, R2}
+   BX      LR ; Return from wait
+   ALIGN
+   END
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