;------------------------------------------------------------------------------------------------------
; Module 7: Design and Implementation of an AHB UART peripheral
; 1)Display text string: "TEST" on VGA. 
; 2)Receive/ print characters from/ to a computer through UART port.
;------------------------------------------------------------------------------------------------------


; Vector Table Mapped to Address 0 at Reset

						PRESERVE8
                		THUMB

        				AREA	RESET, DATA, READONLY	  			; First 32 WORDS is VECTOR TABLE
        				EXPORT 	__Vectors
					
__Vectors		    	DCD		0x0000FFFC
        				DCD		Reset_Handler
        				DCD		0  			
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD 	0
        				DCD		0
        				DCD		0
        				DCD 	0
        				DCD		0
        				
        				; External Interrupts
						        				
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
        				DCD		0
              
                AREA |.text|, CODE, READONLY
;Reset Handler
Reset_Handler   PROC
                GLOBAL Reset_Handler
                ENTRY

				LDR 	R2, =0x50000000
				MOVS	R0,#0x77
				STR		R0, [R2]

;Write "TEST" to the UART

Again
				
				LDR 	R2, =0x51000000
				MOVS	R0, #'\n'
				STR		R0, [R2]

				LDR 	R2, =0x51000000
				MOVS	R0, #'\r'
				STR		R0, [R2]


				LDR 	R2, =0x51000000
				MOVS	R0, #'T'
				STR		R0, [R2]

				LDR 	R2, =0x51000000
				MOVS	R0, #'E'
				STR		R0, [R2]

				LDR 	R2, =0x51000000
				MOVS	R0, #'S'
				STR		R0, [R2]
				
				LDR 	R2, =0x51000000
				MOVS	R0, #'T'
				STR		R0, [R2]

				LDR 	R2, =0x51000000
				MOVS	R0, #':'
				STR		R0, [R2]


;wait until receive buffer is not empty

WAIT			LDR 	R1, =0x51000004
				LDR		R0, [R1]
				MOVS	R1, #01
				ANDS	R0,  R0,  R1
				CMP		R0,	#0x00
				BNE		WAIT		

;print received text to UART

				LDR 	R1, =0x51000000
				LDR 	R2, =0x50000000

				LDR 	R0, [R1]
				STR		R0, [R1]
				STR		R0, [R2]

				B		Again

				ENDP

				ALIGN 		4					 ; Align to a word boundary

		END