; GPIO Port 0 Register address, exercise 7a
;
IO0DIR	EQU	0xE0028008
IO0SET	EQU	0xE0028004
IO0CLR	EQU	0xE002800C
IO0PIN	EQU	0xE0028000
;
RED_LED  EQU 0x00400000; p0.22=RED LED
SW1 	 EQU 0x00100000; p0.20 as SW1
;
;-------------------------------------------------------------
; User Initial Stack & Heap
         AREA    |.text|, CODE, READONLY
;Question (a): When SW1  is depressed,
;When SW1  is depressed write the reg. values (R1,R2,R3,NZVC) 
;   after each line is executed
;Question (b):Repeat the above exercise when SW1 is not depressed

	EXPORT __main						;R0, R1, R3, NZVC
__main							;line1
     LDR R1, =RED_LED; p0.22 as output	                ;line2
     LDR R0, =IO0DIR					;line3
     STR R1,[R0];					;line4
loop LDR R3, =IO0PIN; read SW1 (p0.22)			;line5 
     LDR  R3, [R3]	 			 	;line6
     TST  R3, #SW1;if SW1 depressed R3=0		;line7
     BEQ  onled ;if SW1 depressed LEDon 		;line8
;
	 LDR R1, =RED_LED;otherwise LEDoff		;line9
	 LDR R0, =IO0CLR				;line10
     STR R1,[R0]					;line11
	 B loop						;line12
onled;------ON LED---------
     LDR R1, =RED_LED; on the LED			;line13
     LDR R0, =IO0SET					;line14
     STR R1,[R0]					;line15
     B loop 						;line16
     END