comm

ES/Lab/Lab2/swap/LOOP.asm

@@ -1,26 +1,79 @@
-	AREA RESET, DATA, READONLY
-	EXPORT __Vectors
-__Vectors
-	DCD 0x10001000
-	DCD Reset_Handler
-	ALIGN
-	AREA mycode,CODE,READONLY
-	ENTRY
-	EXPORT Reset_Handler
-Reset_Handler
-	LDR R0, =SRC
-	LDR R1, =DST
-	MOV R2,#10
-BACK
-	LDR R3,[R0],#4;
-	STR R3,[R1],#04;
-	SUBS R2,#1
-	BNE BACK
+; ========================================================================================
+; LOOP.asm - Efficient Array Copy Using Loop Construct
+; ========================================================================================
+; This program demonstrates an efficient way to copy data from one array to another
+; using a loop construct. This approach is much more scalable and maintainable
+; compared to individual copy operations, especially for larger arrays.
 
+	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
+; ========================================================================================
+; Algorithm Overview:
+; 1. Initialize array pointers (R0 = SRC address, R1 = DST address)
+; 2. Set loop counter R2 to the number of elements to copy (10)
+; 3. In each iteration of the loop:
+;    a. Load element from SRC array using post-increment addressing
+;    b. Store element to DST array using post-increment addressing
+;    c. Decrement counter and check if more iterations are needed
+; 4. This approach is much more efficient than individual operations for large arrays
+Reset_Handler
+	; Step 1: Initialize array pointers
+	; R0 points to the beginning of the source array
+	LDR R0, =SRC                      ; R0 = address of first element in SRC array
+
+	; R1 points to the beginning of the destination array
+	LDR R1, =DST                      ; R1 = address of first element in DST array
+
+	; Step 2: Initialize loop counter
+	; R2 holds the number of elements to copy (10 elements total)
+	MOV R2,#10                        ; R2 = 10 (number of elements to copy)
+
+	; Step 3: Main copy loop
+BACK
+	; Load from SRC array and advance pointer
+	; LDR R3, [R0], #4 means: R3 = [R0], then R0 = R0 + 4
+	LDR R3,[R0],#4                    ; Load next element from SRC and advance R0
+
+	; Store to DST array and advance pointer
+	; STR R3, [R1], #4 means: [R1] = R3, then R1 = R1 + 4
+	STR R3,[R1],#04                   ; Store element to DST and advance R1
+
+	; Decrement loop counter and set condition flags
+	SUBS R2,#1                        ; R2 = R2 - 1 (set flags for branch condition)
+
+	; Branch back to BACK if R2 is not zero
+	BNE BACK                          ; If R2 != 0, continue loop
+
+	; Step 4: Program termination
+	; Create an infinite loop to stop program execution
 STOP
-	B STOP
-	ALIGN
+	B STOP                            ; Branch to STOP label (infinite loop)
+
+	ALIGN                             ; Ensure proper alignment for data section
+
+; ========================================================================================
+; Data Section - Source and Destination Arrays
+; ========================================================================================
+; SRC array contains 10 elements (40 bytes total):
+; Each element is a 32-bit word in hexadecimal format
 SRC DCD 0x00000032, 0x12345644, 0x00000005, 0x00000098, 0x000000AB, 0x000000CD, 0x00000055, 0x00000032, 0x000000CA, 0x00000045
-	AREA mydate, DATA, READWRITE
+
+	AREA mydate, DATA, READWRITE      ; Define a read-write data section
+
+; DST array - initially contains space for one element, but will be expanded
+; during copy operations. The loop will copy all 10 elements from SRC to DST
 DST DCD 0
-	END
+
+	END                               ; End of the assembly program