What does LDR do in assembly?
The LDR pseudo-instruction is used for two main purposes: to generate literal constants when an immediate value cannot be moved into a register because it is out of range of the MOV and MVN instructions. to load a program-relative or external address into a register.
What does LDR mean arm?
Memory Instructions: Load and Store (Part 4) | Azeria Labs. Memory Instructions: Load and Store. ARM uses a load-store model for memory access which means that only load/store (LDR and STR) instructions can access memory.
What is ADR in ARM assembly?
The ADR instruction loads an address within a certain range, without performing a data load. ADR accepts a PC-relative expression, that is, a label with an optional offset where the address of the label is relative to the PC.
What is the maximum and minimum signed value that an ARM register can hold?
Since the registers are 32-bit wide, they can hold values from 0 +4294967295 or signed values from -2147483648 .. +2147483647. Bits are numbered 0 to 31, where 0 is the least significant bit, bit 31 is the most significant bit.
What is SWI in arm?
The Software Interrupt instruction (SWI) is used to enter Supervisor mode, usually to request a particular supervisor function.
How does BNE work?
BNE (short for “Branch if Not Equal”) is the mnemonic for a machine language instruction which branches, or “jumps”, to the address specified if, and only if the zero flag is clear.
What is the difference between LDR and LDRB?
LDRSB (Load Register Signed Byte) loads a byte from memory, sign-extends it to form a 32-bit word, and writes the result to a general-purpose register. 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 the difference between LDR and ADR?
LDR obtains the immediate data by putting the data in the program code and uses a PC relative load to get the data into the register. ADR tries to generate the immediate value by adding or subtracting instructions (for example, based on the current PC value).
What is DCB in arm?
The DCB directive allocates one or more bytes of memory, and defines the initial runtime contents of the memory.
Does ARM have a zero register?
The zero register (WZR/XZR) is used for a few encoding tricks. The instruction MUL W0, W1, W2 is identical to MADD W0, W1, W2, WZR which uses the zero register. Not all instructions can use the XZR/WZR. As we mentioned in , the zero register shares the same encoding as the stack pointer.
What are the data types supported by ARM processor?
ARM core data types and arithmetic
- 32-bit pointers.
- unsigned or signed 32-bit integers.
- unsigned 16-bit or 8-bit integers, held in zero-extended form.
- signed 16-bit or 8-bit integers, held in sign-extended form.
- two 16-bit integers packed into a register.
- four 8-bit integers packed into a register.
What is use of SWI in ARM assembly?
Software Interrupt (SWI) functions are functions that run in Supervisor Mode of ARM7™ and ARM9™ core and are interrupt protected. When executing the SWI instruction, the controller changes the running mode to a Supervisor Mode and blocks any further IRQ interrupt requests.