79 lines
No EOL
3.9 KiB
NASM
79 lines
No EOL
3.9 KiB
NASM
; ========================================================================================
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; LOOP.asm - Efficient Array Copy Using Loop Construct
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; ========================================================================================
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; This program demonstrates an efficient way to copy data from one array to another
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; using a loop construct. This approach is much more scalable and maintainable
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; compared to individual copy operations, especially for larger arrays.
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AREA RESET, DATA, READONLY ; Define a read-only data section for the vector table
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EXPORT __Vectors ; Export the vector table for external linking
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__Vectors ; Start of the vector table
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DCD 0x10001000 ; Stack pointer initial value (points to top of stack)
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DCD Reset_Handler ; Address of the reset handler (program entry point)
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ALIGN ; Ensure proper alignment for the next section
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AREA mycode,CODE,READONLY ; Define the code section as read-only
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ENTRY ; Mark the entry point of the program
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EXPORT Reset_Handler ; Export the reset handler function
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; ========================================================================================
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; Reset_Handler - Main program execution
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; ========================================================================================
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; Algorithm Overview:
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; 1. Initialize array pointers (R0 = SRC address, R1 = DST address)
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; 2. Set loop counter R2 to the number of elements to copy (10)
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; 3. In each iteration of the loop:
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; a. Load element from SRC array using post-increment addressing
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; b. Store element to DST array using post-increment addressing
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; c. Decrement counter and check if more iterations are needed
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; 4. This approach is much more efficient than individual operations for large arrays
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Reset_Handler
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; Step 1: Initialize array pointers
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; R0 points to the beginning of the source array
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LDR R0, =SRC ; R0 = address of first element in SRC array
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; R1 points to the beginning of the destination array
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LDR R1, =DST ; R1 = address of first element in DST array
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; Step 2: Initialize loop counter
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; R2 holds the number of elements to copy (10 elements total)
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MOV R2,#10 ; R2 = 10 (number of elements to copy)
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; Step 3: Main copy loop
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BACK
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; Load from SRC array and advance pointer
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; LDR R3, [R0], #4 means: R3 = [R0], then R0 = R0 + 4
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LDR R3,[R0],#4 ; Load next element from SRC and advance R0
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; Store to DST array and advance pointer
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; STR R3, [R1], #4 means: [R1] = R3, then R1 = R1 + 4
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STR R3,[R1],#04 ; Store element to DST and advance R1
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; Decrement loop counter and set condition flags
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SUBS R2,#1 ; R2 = R2 - 1 (set flags for branch condition)
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; Branch back to BACK if R2 is not zero
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BNE BACK ; If R2 != 0, continue loop
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; Step 4: Program termination
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; Create an infinite loop to stop program execution
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STOP
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B STOP ; Branch to STOP label (infinite loop)
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ALIGN ; Ensure proper alignment for data section
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; ========================================================================================
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; Data Section - Source and Destination Arrays
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; ========================================================================================
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; SRC array contains 10 elements (40 bytes total):
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; Each element is a 32-bit word in hexadecimal format
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SRC DCD 0x00000032, 0x12345644, 0x00000005, 0x00000098, 0x000000AB, 0x000000CD, 0x00000055, 0x00000032, 0x000000CA, 0x00000045
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AREA mydate, DATA, READWRITE ; Define a read-write data section
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; DST array - initially contains space for one element, but will be expanded
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; during copy operations. The loop will copy all 10 elements from SRC to DST
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DST DCD 0
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END ; End of the assembly program |