Table of Contents
What does LDR R0 R1 mean?
A register contains the memory address of (points to) the data. Address equivalent to an index into the array of memory bytes. LDR R0,[R1] ; R0= value pointed to by R1.
What are the addressing modes in ARM?
The ARM processor (Thumb-2), part 3: Addressing modes
| Mnemonic | Meaning | Notes |
|---|---|---|
| LSL #imm | Logical shift left | Shift left with zero-fill |
| LSR #imm | Logical shift right | Shift right with zero-fill |
| ASR #imm | Arithmetic shift right | Shift right with sign-fill |
| ROR #imm | Rotate right | 32-bit rotation |
What is the difference between post indexing and pre indexing?
These are two forms of addressing, both of which involve indirect addressing and indexing. With preindexing, the indexing is performed before the indirection. With postindexing, the indexing is performed after the indirection.
What is pre-indexed addressing mode?
The pre-indexed addressing mode provides a means of simplifying the process be eliminating the ADD instructions. LDR. r0, [r1, #4] ; load r0 with the value found at the memory. ; location whose address is the value of r1 + 4.
What is ARM instruction format?
They are move, arithmetic, logical, comparison and multiply instructions and multiply instructions.
Why is it called register indirect?
Register indirect addressing means that the location of an operand is held in a register. It is also called indexed addressing or base addressing. Register indirect addressing mode requires three read operations to access an operand.
What is a Thumb instruction in ARM?
The Thumb instruction set is a subset of the most commonly used 32-bit ARM instructions. Thumb instructions are each 16 bits long, and have a corresponding 32-bit ARM instruction that has the same effect on the processor model.
What is indexed addressing?
indexed addressing (indexing) A method of generating an effective address that modifies the specified address given in the instruction by the contents of a specified index register. The modification is usually that of addition of the contents of the index register to the specified address.
What is LSL in ARM?
ARM has two logical shift operations, namely LSL (Logical Shift Left) and LSR (Logical Shift Right). LSL is a logical shift left by 0 to 31 places. The vacated bits at the least significant end of the word are filled with zeros.
What does LDRB mean in assembly?
Load Register Byte
LDRB (Load Register Byte) loads a byte from memory, zero-extends it to form a 32-bit word, and writes the result to a general-purpose register.
What is arm7 and arm8?
The ARMv7 architecture is the basis for all current 32-bit ARM Cortex™ processors, including the Cortex-A15 and Cortex-A9 processors. The ARMv8 architecture is the first ARM architecture that includes 64-bit execution, enabling processors based on the architecture to combine 64-bit execution with 32-bit execution.
What is arm7 and ARM64?
Within a given architecture type there are multiple versions. armeabi-v7a is the older target, for 32 bit arm cpus, almost all arm devices support this target. arm64-v8a is the more recent 64 bit target (similar to the 32-bit -> 64 bit transition in desktop computers). I think most new devices are 64 bit, but not sure.
What is pre indexing in ARM?
Pre-indexed. The offset is added to or subtracted from the base register to form the memory address. The base register is then updated with this new address, to permit automatic indexing through an array or memory block. Post-indexed. The value of the base register alone is used as the memory address.
What are the three architecture profiles of an ARM processor?
The architecture has evolved over time, and version seven of the architecture, ARMv7, defines three architecture “profiles”: A-profile, the “Application” profile, implemented by 32-bit cores in the Cortex-A series and by some non-ARM cores. R-profile, the “Real-time” profile, implemented by cores in the Cortex-R series.