99 lines
No EOL
5.1 KiB
NASM
99 lines
No EOL
5.1 KiB
NASM
; ========================================================================================
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; MULTINDEX.asm - Mixed Addressing Modes for Array Copy Operations
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; ========================================================================================
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; This program demonstrates different addressing modes used in ARM assembly for
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; array operations. It intentionally mixes various approaches to show the
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; different ways memory can be accessed and how pointers are managed.
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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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; This program demonstrates various addressing modes for copying array elements:
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; 1. Basic load/store without pointer advancement
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; 2. Post-increment addressing (! symbol) - pointer advances after operation
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; 3. Pre-indexed addressing without (!) - pointer doesn't advance automatically
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; 4. Mixed approaches to show flexibility in ARM assembly programming
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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: Copy first element - Basic addressing (no pointer advancement)
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; Load from [R0] and store to [R1] without changing pointer values
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LDR R2,[R0] ; R2 = SRC[0] (R0 unchanged)
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STR R2,[R1] ; DST[0] = R2 (R1 unchanged)
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; Step 3: Copy next 3 elements - Post-increment addressing
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; Using '!' symbol means pointer is updated after the operation
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LDR R3,[R0,#4]! ; R3 = SRC[1], then R0 = R0 + 4
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STR R3,[R1,#4]! ; DST[1] = R3, then R1 = R1 + 4
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LDR R4,[R0,#4]! ; R4 = SRC[2], then R0 = R0 + 4
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STR R4,[R1,#4]! ; DST[2] = R4, then R1 = R1 + 4
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LDR R5,[R0,#4]! ; R5 = SRC[3], then R0 = R0 + 4
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STR R5,[R1,#4]! ; DST[3] = R5, then R1 = R1 + 4
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; Step 4: Copy next 3 elements - Pre-indexed addressing without advancement
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; Without '!' symbol, pointers are not automatically updated
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; Manual pointer advancement is needed (not shown here, which may be intentional)
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LDR R6,[R0,#4] ; R6 = SRC[4] (R0 unchanged)
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STR R6,[R1,#4] ; DST[4] = R6 (R1 unchanged)
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LDR R7,[R0,#4] ; R7 = SRC[5] (R0 unchanged)
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STR R7,[R1,#4] ; DST[5] = R7 (R1 unchanged)
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LDR R8,[R0,#4] ; R8 = SRC[6] (R0 unchanged)
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STR R8,[R1,#4] ; DST[6] = R8 (R1 unchanged)
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; Step 5: Copy last 3 elements - Post-increment addressing again
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; Switch back to post-increment mode for the final elements
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LDR R9,[R0],#4 ; R9 = SRC[7], then R0 = R0 + 4
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STR R9,[R1],#4 ; DST[7] = R9, then R1 = R1 + 4
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LDR R10,[R0],#4 ; R10 = SRC[8], then R0 = R0 + 4
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STR R10,[R1],#4 ; DST[8] = R10, then R1 = R1 + 4
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LDR R11,[R0],#4 ; R11 = SRC[9], then R0 = R0 + 4
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STR R11,[R1],#4 ; DST[9] = R11, then R1 = R1 + 4
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; Step 6: 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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; Note: The middle section (elements 4-6) uses pre-indexed addressing without
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; pointer advancement, which means the same memory locations are accessed
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; multiple times. This demonstrates different addressing mode behaviors.
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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 to accommodate all 10 elements
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DST DCD 0
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END ; End of the assembly program |