Instruction Syntax

Mnemonic	Format	Flags
stb	rS,d(rA)	None

Instruction Encoding

Field	Bits	Description
Primary Opcode	0-5	100110 (0x26)
rS	6-10	Source register
rA	11-15	Base register
SIMM	16-31	Signed immediate offset

Operation

EA ← (rA) + SIMM
(EA) ← (rS)[24:31]

The effective address is calculated by adding the signed immediate offset to the base register. The least significant byte of the source register is stored at the effective address.

Note: The stb instruction stores the least significant byte (bits 24-31) of the source register to memory.

Affected Registers

Memory

• Byte at effective address (EA)

Examples

Basic Store Byte

# Store byte from r3 to address in r4
stb r3, 0(r4)      # Store byte at address in r4
stb r3, 4(r4)      # Store byte at address r4 + 4

Array Access

# Store byte in array
li r4, 0           # Array index
slwi r4, r4, 0     # Multiply by 1 (byte size)
add r5, r3, r4     # Calculate address
stb r6, 0(r5)      # Store byte

Character Storage

# Store character in string
li r3, 'A'         # Load character 'A'
stb r3, 0(r4)      # Store at string address
li r3, 0           # Null terminator
stb r3, 1(r4)      # Store null terminator

Related Instructions

stbu, stbux, stbx, lbz