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Load Register Byte (unscaled) calculates an address from a base register and an immediate offset, loads a byte from memory, zero-extends it, and writes it to a register. For information about memory accesses, see Load/Store addressing modes.


Unscaled offset

LDURB <Wt>, [<Xn|SP>{, #<simm>}]

bits(64) offset = SignExtend(imm9, 64);

Assembler Symbols


Is the 32-bit name of the general-purpose register to be transferred, encoded in the "Rt" field.


Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field.


Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0 and encoded in the "imm9" field.

Shared Decode

integer n = UInt(Rn);
integer t = UInt(Rt);

boolean tag_checked = n != 31;


if HaveMTEExt() then

bits(64) address;
bits(8) data;

if n == 31 then
    address = SP[];
    address = X[n];

address = address + offset;

data = Mem[address, 1, AccType_NORMAL];
X[t] = ZeroExtend(data, 32);

Operational information

If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.