ARM study notes 4 - load and store instructions

1. Word data transfer instruction

Function: Used to transfer single data into or out of a register.

　　1. LDR instruction

　　　　1.1. Function

　　　　　　Read a 32-bit field from memory to the target register according to the address mode determined by . If the address determined by the addressing mode in the instruction is not word-aligned, the read value must be circularly shifted right.

　　　　1.2 Syntax format

　　　　　　LDR{} ,

　　　　1.3 Parameter Description

　　　　　　 determines which general register to use as the destination register

　　　　　　 determines the I, P, U, W, Rn and bits in the instruction encoding

　　2. STR instruction

　　　　2.1. Function

　　　　　　Write a 32-bit word of data to the memory location specified in the instruction

　　　　2.2 Syntax format

　　　　　　STR{} ,

2. Byte data transfer instruction (LDRB/STRB)

　　1. LDRB instruction

　　　　1.1. Function

　　　　　　Read an 8-bit byte into the destination register in the instruction according to the address mode determined by

　　　　1.2. Syntax format LDR{}B ,

　　2. STRB instruction

　　　　2.1. Function

　　　　　　Take the specified 8-bit byte from the register and put it into the lower 8 bits of the memory unit specified in the instruction, and fill its high bits with 0

　　　　2.2 Syntax format STR{}B ,

3. Half-word data transfer instruction (LDRH/STRH)

　　1. LDRH

　　　　1.1. Function

　　　　　　Read a 16-bit halfword from memory into the destination register.

　　　　1.2 Syntax format

　　　　　　LDR{}H ,

　　2. STRH

　　　　2.1. Function

　　　　　　Take the 16-bit half word from the register and put it into the lower 16 bits of the memory unit specified in the instruction, and fill its high bits with 0

　　　　2.2 Syntax format

　　　　　　STR{}H ,

4. User mode word data transfer instructions

　　1. LDRT

　　　　1.1. Function

　　　　　　In user mode, read a 32-bit word from memory to the destination register according to the address mode determined by

　　　　1.2 Syntax format

　　　　　　LDR{}T ,

　　　　1.3 Parameter Description

　　　　　　: Use post-indexed address mode addressing

　　2. STRT

　　　　2.1. Function

　　　　　　Write a 32-bit word of data to the memory location specified in the instruction

　　　　2.2 Syntax format

　　　　　　STR{}T ,

5. User mode byte data transfer instructions

　　1. LDRBT instruction

　　　　1.1. Function

　　　　　　Read an 8-bit byte into the destination register in the instruction according to the addressing mode

　　　　1.2 Syntax format

　　　　　　LDR{}BT ,

　　2. STRBT instruction

　　　　2.1. Function

　　　　　　Write an 8-bit byte of data to the memory location specified in the instruction

　　　　2.2 Syntax format

　　　　　　STR{}BT ,,

6. Signed byte/half-word data transfer instructions

　　1. LDRSB instruction

　　　　1.1. Function

　　　　　　Read an 8-bit byte into the destination register in the instruction according to the address mode determined by

　　　　1.2 Syntax format

　　　　　　LDR{}SB ,

　　2. LDRSH instruction

　　　　2.1. Function

　　　　　　Read a 16-bit halfword into the destination register in the instruction according to the address mode determined by

　　　　2.2 Syntax format

　　　　　　LDR{}SH ,