Write assembly language code to program KL25Z (ARM cortex M0+) transfer the data with memory.

 

   TTL mem_transfer                                ; give name to the file
        AREA Myprog, CODE, READONLY  ; defining name to the

ENTRY
        EXPORT main                                        ; Export address of main to MKL25Z4.s
main         

;---------------------------------------------------------------------------------------------------------                          ;Prerequisite
; Register R0-R7 can only use
;For half word transfer 0th bit of source address must be 0, to avoid HARDfault exception
;For word transfer 0th and 1st both bits of source address must be 0, to avoid HARDfault exception
; Read page no 132, note for the same of ARM cortex M0 and M0+ definitive guide.

; R7=0x1FFFF100 it is already memory mapped, if you take any other value you need to go to debug ;and need to memory map manually for reading and writing.

;Part-1 register offset addressing mode

        LDR R7, =0x1FFFF100   ;load value of "top of the stack" into R7=address of stack area
        LDR R1,=0x00                 ;r1=00
        LDRB R2,[R7,R1]           ;Byte transfer R2= memory (R7+R1)
        LDR R1,=0x02                ; TO avoide HARD fault exception 0th bit always 0 while transferring ;half word
        LDRH R3,[R7,R1]          ;Half word transfer R2= memory (R7+R1)
        LDR R1,=0x04                ;TO avoide HARD fault exception 0th, 1st bits always 0 while ;transferring word
        LDR R4,[R7, R1]        ;Word transfer R2= memory (R7+R1)

;Part-2 immediate offset addressing mode

        LDRB R5, [R7,#0x00]      ;R5=R7+0x00
        LDRH R6, [R7,#0x02]     ;R6=R7+(0x02)
        LDR R2, [R7,#0x04]        ;R6=R7+(0x04)
        
;Part-3 Stack pointer
        LDR R3, [SP,#0x00]    ; R3= SP(0x1FFFF160)+0x04

;Part-4 Sign extended Load
        LDR R1,=0x02
        LDRSH R4,[R7, R1]
        LDR R1,=0x03
        LDRSB R5,[R7, R1]
;part-5 Store the values to the memory location with relative register

        LDR R1,=0x08          ; to get the proper offset for Store operation leave first locations
        STRB R2, [R7, R1]   ; memory[R7+R1] = R2
        LDR R1,=0x0A         ; R1=0X0A
        STRH R3,[R7,R1]     ; memory[R7+R1] = R3
        LDR R1,=0x0C         ; R1=0x0C
        STR R4,[R7,R1]        ; memory[R7+R1] = R4
        
;Part-6 Store the value to the memory location with relative immediate address

        STRB R5,[R7,#0x0D]
        STRH R6,[R7,#0x0E]
        STR R2,[R7,#0x10]

;Part-7 Store the value to the memory location with SP relative address

        STR R3, [SP,#0x04] ; Store word on memory location form by [SP+4] = R3

done

        SWI &11 ; go to system subroutine write on location 11
        END        ;End of the code

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;Now you need to save the file-> Build the project -> debug it it and.

; prior to start debug follow below steps

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; in memory window of the keil micro vision enter address 0x1FFFF100.

; enter random data in to eight sub subsequent addresses, to observe the result

;to observe the result of this LDR R3, [SP,#0x00]; instruction we need to enter values in to 4

; subsequent 8bit data starting from 0x1FFFF160 to 0x1FFFF163 .

 ;--------------------------------------------------------------------------------------------------------------------