lbz

Load Byte and Zero

lbz RT, D(RA)

Loads a byte from memory into the low 8 bits of a register and clears the upper 56 bits.

Details

The effective address (EA) is computed as the sum of the contents of register RA and the sign-extended immediate value D. The byte at EA is loaded into RT, with the upper 56 bits set to zero.

Pseudocode Operation

if 'lbz' then
    EA ← (RA|0) + EXTS64(D)
    RT ← EXTZ(MEM(EA, 1))

Programming Note

The lbz instruction is commonly used for loading a single byte from memory into a register while zeroing out the upper bits. Ensure that the address is properly aligned to avoid potential performance penalties or exceptions. This instruction operates at user privilege level and will raise an exception if the EA is outside the valid address space.

Example

lbz r3, 0(r4)

Encoding

Binary Layout
34
0
RT
6
RA
11
D
16
 
Format D-form
Opcode 0x88000000
Extension Base

Operands

  • RT
    Target Register
  • D
    Displacement (16-bit Signed)
  • RA
    Base Register