;*-------------------------------------------------------------------
;* Name:    	lab_4_program.s
;* Purpose: 	A sample style for lab-4
;* Term:		Winter 2013
;*-------------------------------------------------------------------
				THUMB 								; Declare THUMB instruction set
				AREA 	My_code, CODE, READONLY 	;
				EXPORT 		__MAIN 					; Label __MAIN is used externally

				ENTRY

__MAIN
				LDR			R10, = ISER0
				LDR			R1, [R10]
				ORR			R1, R1, #0x200000         ; setting bit 21 of ISER0
				STR			R1, [R10]					; store the  value into ISER0 to enable EINT3
				MOV			R6, #0x1					; R6 is getting set a as a flag, 1 when not pressed, 0 when pressed
				LDR			R10, = IO2IntEnf
				LDR			R1, [R10]
				ORR			R1, R1, #0x400
				STR			R1, [R10]
				; falling edge because that's when the button is pressed, raising edge doesn't record this

; The following lines are similar to previous labs.
; They just turn off all LEDs
				LDR			R10, =LED_BASE_ADR		; R10 is a  pointer to the base address for the LEDs
				MOV 		R3, #0xB0000000		; Turn off three LEDs on port 1
				STR 		R3, [r10, #0x20]
				MOV 		R3, #0x0000007C
				STR 		R3, [R10, #0x40] 	; Turn off five LEDs on port 2


; This line is very important in your main program
; Initializes R11 to a 16-bit non-zero value and NOTHING else can write to R11 !!
				MOV			R11, #0xABCD		; Init the random number generator with a non-zero number
				BL 			RNG
				; going to use R12 and so on
				MOV			R2, R11
				AND			R2, R2, #0x7			; Take last 3 bits of R11 (#0x7 = 111 in binary)
				ADD			R2, R2, #2				; AND to store last 3 bits of R11 in R5
				AND			R3, R11, #0x10			; Take 4th bit of R11
				LSR			R3, R3, #4				; Shift it to make the bit LSB for adding
				ADD			R2, R2, R3				; After adding, R5 has random number between 2-10
				MOV			R3, #10000
				MUL			R2, R2, R3				; Multiply R5 by 10000
				ADD			R0, R2, #0				; Store into R0 for delay decrementer
				MOV         R9, #0x007D
				MOVT        R9, #0x0				; Takes 0.1 ms (approx) to subtract to 0
				MUL			R0, R9, R0				; R0 now has a number that takes between 2-10 seconds to subtract to 0
				BL			LED_ALT






		;
		; Your main program can appear here
		;

; 4C4B4 for 0.25 second
; try not to use R6
; 4FFFFF83 for turning all of them on
; need some work
LED_ALT			STMFD		R13!, {R1-R12, R14}
				MOV			R4, #0xC4B4
				MOVT		R4, #0x0004
				MOV 		R5, R0            ; copy over the value of R0
				MOV			R0, R4			 ; calls the .25 delay
				BL          DELAY							; call DELAY
				SUBS		R5, R5, R4
				ADD			R0, R5, #0
				BL			LED_OFF
				; for lighting the second four (left side)
				MOV			R3, #0xFFFB
				MOVT		R3, #0x4FFF
				STR			R3, [R10, #0x20]
				STR			R3, [R10, #0x40]
				MOV			R4, #0xC4B4
				MOVT		R4, #0x0004
				MOV 		R5, R0            ; copy over the value of R0
				MOV			R0, R4			 ; calls the .25 delay
				BL          DELAY							; call DELAY
				SUBS		R5, R5, R4
				ADD			R0, R5, #0
				BL			LED_OFF
				; for lighting the first four (right side)
				MOV			R3, #0x00000004
				STR			R3, [R10, #0x40]
				BLT			LED_ALT
				LDMFD		R13!, {R1-R12, R15}

LED_OFF			STMFD 		R13!, {R3, R14}
				MOV 		R3, #0xB0000000			; Turn off three LEDs on port 1
				STR 		R3, [R10, #0x20]    	; Write the necessary bits to turn off the LED on port 1
				MOV 		R3, #0x0000007C     	; Move the necessary number for turning off port 2
				STR 		R3, [R10, #0x40] 		; Turn off five LEDs on port 2
				LDMFD 		R13!, {R3, R15}
;*-------------------------------------------------------------------
; Subroutine RNG ... Generates a pseudo-Random Number in R11
;*-------------------------------------------------------------------
; R11 holds a random number as per the Linear feedback shift register (Fibonacci) on WikiPedia
; R11 MUST be initialized to a non-zero 16-bit value at the start of the program
; R11 can be read anywhere in the code but must only be written to by this subroutine
RNG 			STMFD		R13!,{R1-R3, R14} 	; Random Number Generator
				AND			R1, R11, #0x8000
				AND			R2, R11, #0x2000
				LSL			R2, #2
				EOR			R3, R1, R2
				AND			R1, R11, #0x1000
				LSL			R1, #3
				EOR			R3, R3, R1
				AND			R1, R11, #0x0400
				LSL			R1, #5
				EOR			R3, R3, R1			; The new bit to go into the LSB is present
				LSR			R3, #15
				LSL			R11, #1
				ORR			R11, R11, R3
				LDMFD		R13!,{R1-R3, R15}

;*-------------------------------------------------------------------
; Subroutine DELAY ... Causes a delay of 1ms * R0 times
;*-------------------------------------------------------------------
DELAY			STMFD		R13!,{R0, R14}
;				MUL			R9, R9, R0				; code to generate a delay of 0.1mS * R0 times
loopDelay       SUBS        R0, R0, #1      		; Keep subtracting until we have reached 0
                BNE         loopDelay
		;
exitDelay		LDMFD		R13!,{R0, R15}

; The Interrupt Service Routine MUST be in the startup file for simulation
;   to work correctly.  Add it where there is the label "EINT3_IRQHandler
;
;*-------------------------------------------------------------------
; Interrupt Service Routine (ISR) for EINT3_IRQHandler
;*-------------------------------------------------------------------
; This ISR handles the interrupt triggered when the INT0 push-button is pressed
; with the assumption that the interrupt activation is done in the main program
EINT3_IRQHandler
					;STMFD 		... 				; Use this command if you need it
		;
		; Code that handles the interrupt
		;
					;LDMFD 		... 				; Use this command if you used STMFD (otherwise use BX LR)
				MOV			R6, #0x00                ; clearing the interrupt
				LDR			R10, =IO2IntEnf
				LDR			R1, [R10]
				EOR			R1, R1, #0X400
				STR			R1, [R10]
				BX 			LR


;*-------------------------------------------------------------------
; Below is a list of useful registers with their respective memory addresses.
;*-------------------------------------------------------------------
LED_BASE_ADR	EQU 	0x2009c000 		; Base address of the memory that controls the LEDs
PINSEL3			EQU 	0x4002C00C 		; Pin Select Register 3 for P1[31:16]
PINSEL4			EQU 	0x4002C010 		; Pin Select Register 4 for P2[15:0]
FIO1DIR			EQU		0x2009C020 		; Fast Input Output Direction Register for Port 1
FIO2DIR			EQU		0x2009C040 		; Fast Input Output Direction Register for Port 2
FIO1SET			EQU		0x2009C038 		; Fast Input Output Set Register for Port 1
FIO2SET			EQU		0x2009C058 		; Fast Input Output Set Register for Port 2
FIO1CLR			EQU		0x2009C03C 		; Fast Input Output Clear Register for Port 1
FIO2CLR			EQU		0x2009C05C 		; Fast Input Output Clear Register for Port 2
IO2IntEnf		EQU		0x400280B4		; GPIO Interrupt Enable for port 2 Falling Edge
ISER0			EQU		0xE000E100		; Interrupt Set-Enable Register 0

				ALIGN

				END