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Questions and Answers
What is a key feature of the ARM instruction set architecture?
How many operands can be processed in a single data processing instruction?
What is the result size of a multiply instruction in ARM?
What is the purpose of the condition field in ARM instructions?
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What is the effect of the MOVS instruction on the flags?
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How many possible machine instructions are there in ARM?
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What is the purpose of the MVN instruction in the given code?
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What is the effect of the instruction 'MOV R0, R2, ROR #2' on the register R2?
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In the instruction 'ADD R0, R1, R2', what is the role of R1 and R2?
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What is the significance of the bottom 8 bits of the register in shifted register operands?
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What is the difference between the ROR and RRX instructions?
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What is the effect of the instruction 'MOV R0, 0' on the register R0?
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What is the purpose of the 'cond' field in the instruction encoding?
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What is the function of the 'v' field in the instruction encoding?
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What is the range of immediate values that can be loaded using a single instruction?
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What is the purpose of the 'Rn' field in the instruction encoding?
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What is the function of the 'Sh' field in the instruction encoding?
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What is the purpose of the 'Rm' field in the instruction encoding?
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What is the function of the 'opcode' field in the instruction encoding?
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What is the purpose of the 'imm' field in the instruction encoding?
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What is the addressing mode where the calculation is done before accessing the memory with a writeback?
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What is the result of the instruction LDR R0, [R1, #4]?
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Which addressing mode is used in the instruction LDR R0, [R1, R2]?
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What is the effect of the writeback in auto-indexing addressing?
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What is the result of the instruction LDR R0, [R1, R2, LSL #2]?
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What is the difference between pre-index and post-index addressing?
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Which addressing mode is used in the instruction LDR R0, [R1], #4?
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What is the advantage of auto-indexing addressing?
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What is the guideline for loading constants into a register?
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How can you load the value 511 into R0 using the fewest number of instructions?
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What is the purpose of the ADR instruction in the example code?
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What is the mode of addressing used in the instruction 'ldr r0, [pc, #4]'?
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What is the sequence of operations performed by the CPU during the execution of an instruction?
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What is the purpose of the instruction 'SWI #11' in the example code?
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Study Notes
ARM Instruction Set
- 232 possible machine instructions, structured into:
- Load-store architecture
- 3-address instructions
- Conditional execution of every instruction
- Load/store multiple registers at once
- Combine shift and ALU operations in a single instruction
Data Processing
- Instructions: move, arithmetic, logical, comparison, and multiply
- Most data processing instructions process one operand using the barrel shifter
- General rules:
- All operands are 32-bit, coming from registers or literals
- Result is 32-bit and placed in a register (except for long multiply, which produces a 64-bit result)
- 3-address format
Conditional Execution
- Almost all ARM instructions have a condition field, allowing conditional execution
- Example:
MOVCS R0, R1 @ if carry is set, then R0:=R1
Register Movement
- MOV instruction:
MOV R0, R2 @ R0 = R2
- MVN instruction:
MVN R0, R2 @ R0 = ~R2
(move negated)
Addressing Modes
- Register operands:
ADD R0, R0, R1
- Immediate operands:
ADD R0, R0, #4
- Rotate right:
MOV R0, R2, ROR #2 @ R0:=R2 rotate right 2
- Rotate right extended:
MOV R0, R2, RRX @ R0:=R2 rotate right extended
- Shifted register operands: use a register to specify the number of bits to be shifted
Load and Store
- Load:
LDR R0, [R1] @ mem[R1]
- Store:
STR R0, [R1] @ mem[R1]
- Addressing modes:
- Pre-index:
LDR R0, [R1, #4]
- Auto-indexing:
LDR R0, [R1, #4]!
- Post-index:
LDR R0, [R1], #4
- Pre-index:
Comparisons
- Pre-indexed addressing:
LDR R0, [R1, R2] @ R0=mem[R1+R2]
- Auto-indexing addressing:
LDR R0, [R1, R2]! @ R0=mem[R1+R2]
- Post-index addressing:
LDR R0, [R1], R2 @ R0=mem[R1]
Load Constants
- Assemblers implement loading constants using two options:
- Construct it in multiple instructions
- Load it from memory
- Guideline: if you can construct it in two instructions, do it; otherwise, load it
PC-relative Addressing
- Impossible to use direct addressing encoding for data transfer instructions
- Example:
ADR R1, a @ add r1, pc, #4
- PC-relative addressing mode:
LDR R0, [PC, #0]
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Description
This quiz covers ARM assembly language instructions for register movement, addressing modes, and immediate operands. It includes examples of MOV, MVN, and ADD instructions with register and immediate operands.