; ========================================================================================
; DATATRANSFER.asm - Memory-Based Data Transfer Operations Demonstration
; ========================================================================================
; This program demonstrates how to transfer data from memory locations to registers
; using ARM load instructions. It shows the difference between loading an address
; and loading the actual data stored at that address.

	AREA RESET,DATA,READONLY        ; Define a read-only data section for the vector table
	EXPORT __Vectors                ; Export the vector table for external linking

__Vectors                           ; Start of the vector table
	DCD 0x10001000                  ; Stack pointer initial value (points to top of stack)
	DCD Reset_Handler               ; Address of the reset handler (program entry point)
	ALIGN                           ; Ensure proper alignment for the next section

	AREA mycode,CODE,READONLY       ; Define the code section as read-only
	ENTRY                           ; Mark the entry point of the program
	EXPORT Reset_Handler           ; Export the reset handler function

; ========================================================================================
; Reset_Handler - Main program execution
; ========================================================================================
; This function demonstrates memory data transfer operations:
; 1. Load the address of a data array into a register
; 2. Load the actual data from that memory location
; 3. Load an immediate negative value for comparison
Reset_Handler
	; Step 1: Load memory address into register
	; LDR with = syntax loads the address of the SRC array into R0
	; This gives us a pointer to the beginning of the data array
	LDR R0, =SRC                    ; R0 = address of SRC array

	; Step 2: Load data from memory location
	; LDR with [] syntax loads the actual data stored at the address in R0
	; This reads the first 32-bit word from the SRC array (0x12345678)
	LDR R1, [R0]                    ; R1 = data at address in R0 (first element of SRC)

	; Step 3: Load immediate negative value
	; MOV instruction loads the immediate negative value -8 into R5
	; This demonstrates mixing memory loads with immediate loads
	MOV R5, -8                      ; R5 = -8 (immediate negative value)

	; Step 4: Program termination
	; Create an infinite loop to stop program execution
STOP
	B STOP                          ; Branch to STOP label (infinite loop)

	ALIGN                           ; Ensure proper alignment for data section

; ========================================================================================
; Data Section - Source data array
; ========================================================================================
; SRC array contains three 32-bit words in hexadecimal format:
; - First word: 0x12345678 (305419896 in decimal)
; - Second word: 0xABCDEF55 (2882400341 in decimal)
; - Third word: 0x55 (85 in decimal)
SRC DCD 0x12345678, 0xABCDEF55, 0x55

	END                             ; End of the assembly program