Assembler

Load value from registers

### Load Byte value

ADDR_DIP_SWITCH_7_0         EQU     0x60000200

LDR     R0, =ADDR_DIP_SWITCH_7_0 	; read dip switch address into r0
LDRB    R0, [R0]					; read dip switches 15 to 8 into r0

### Load half word value

ADDR_DIP_SWITCH_7_0         EQU     0x60000200

LDR     R0, =ADDR_DIP_SWITCH_7_0 	; read dip switch address into r0
LDRH    R0, [R0]					; read dip switches 15 to 8 into r0

Storing Value

Store byte

ADDR_LED_31_24              EQU     0x60000103

LDR     R6, =ADDR_LED_31_24 		; store led address in R6
STRB    R3, [R6] 					; display array_index

Store halfword

ADDR_SEG7_BIN   			EQU		0x60000114

LDR     R6, =ADDR_SEG7_BIN			; load address
STRH    R0, [r6, #0]				; Store Index and Value to SSD

Bitwise AND

Bitwise and between value and address

BITMASK_LOWER_NIBBLE        EQU     0x0F

LDR		R2, =BITMASK_LOWER_NIBBLE	; read address of lower bitmask nibble
ANDS	R0, R0, R2					; store into r0 <- (r0 and mask: r2)

Incrementing address

Increment R4 by one

ADDS	R4, R4, #1					; increment register address

Shift

Shift Left

LSLS	R1, R1, #1					; increment index by multiplying it x2

Moving Register

MOV		R5, R1						; copy R1 into R5

Type Casting

Sign Extension (signed)

Extend word without changing value

SXTB    R3, R7                     ; extend R7 into R3 (8 bit to 32 bit)
SXTH    R3, R7                     ; extend R7 into R3 (16 bit to 32 bit)

Zero Extension (signed)

Extend word without changing value

UXTB    R3, R7                     ; extend R7 into R3 (8 bit to 32 bit)
UXTH    R3, R7                     ; extend R7 into R3 (16 bit to 32 bit)

Bitmanipulation

OR

ORRS    R3, R7                     ; OR MASK

CLR - Clear Bits

BICS    R3, R7                     ;

XOR - Bitwise invert

EORS    R3, R7                     ;

AND

ANDS    R3, R7                     ;

Bits löschen

ADDRESS      ECU     ...

LDR         R6, =ADDRESS        ; ADDRESSE in R6 laden
LDR         R1, [R6]            ; Wert von R6 in R1 laden
LDR         R2, =0x2220         ; Maske 0x2220 in R2 laden
BICS        R1, R2              ; Bits R2 in R1 löschen
STR         R1, [R6]            ; R1 in R6 schreiben

Kontrollstrukturen

Switch Case


NR_CASES                EQU     0x2

jump_table      ; ordered table containing the labels of all cases
                ; STUDENTS: To be programmed 
				DCD		case_dark
				DCD 	case_add
				DCD		...


case_dark       
                LDR  R0, =0
                B    display_result  

case_add        
                ADDS R0, R0, R1
                B    display_result


                CMP	R2, #NR_CASES
				BHS	case_bright
				LSLS R2, #2		; * 4
				LDR R7,=jump_table
				LDR R7, [R7, R2]
				BX R7

My ZHAW Notes