stb

Store Byte

stb RS, D(RA)

Stores the low 8 bits of a register to memory.

Details

The stb instruction stores the lower byte (bits 56-63) of the contents of register RS into the memory location specified by the effective address EA, which is calculated as (RA|0) + EXTS64(D).

Pseudocode Operation

if 'stb' then
    EA ← (RA|0) + EXTS64(D)
    MEM(EA, 1) ← (RS)56:63

Programming Note

The stb instruction is commonly used to store a single byte from a register into memory. Ensure that the destination address is properly aligned for optimal performance and avoid accessing invalid or protected memory regions to prevent exceptions.

Example

stb r3, 0(r4)

Encoding

Binary Layout
10
0
DS
6
RS
11
RA
16
SIMM[15:0]
 
Format D-form
Opcode 0x98000000
Extension Base

Operands

  • RS
    Source Register
  • D
    Displacement
  • RA
    Base Register
  • EA
    Effective Address