LDURSB Load register signed byte (unscaled) This instruction calculates an address from a base register and an immediate offset, loads a signed byte from memory, sign-extends it, and writes it to a register. For information about addressing modes, see Load/Store addressing modes. This instruction is a data-independent-time instruction as described in About PSTATE.DIT. 0 0 1 1 1 0 0 0 1 x 0 0 0 1 LDURSB <Wt>, [<Xn|SP>{, #<simm>}] 0 LDURSB <Xt>, [<Xn|SP>{, #<simm>}] let offset : bits(64) = SignExtend{}(imm9); <Wt> Is the 32-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. <Xn|SP> Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. <simm> Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0 and encoded in the "imm9" field. <Xt> Is the 64-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. let n : integer = UInt(Rn); let t : integer = UInt(Rt); let datasize : integer{} = 8; let regsize : integer{} = 64 >> UInt(opc[0]); let nontemporal : boolean = FALSE; let tagchecked : boolean = n != 31; var address : bits(64); let privileged : boolean = PSTATE.EL != EL0; let accdesc : AccessDescriptor = CreateAccDescGPR(MemOp_LOAD, nontemporal, privileged, tagchecked, t); if n == 31 then CheckSPAlignment(); address = SP{64}(); else address = X{64}(n); end; address = AddressAdd(address, offset, accdesc); let data : bits(datasize) = Mem{datasize}(address, accdesc); X{regsize}(t) = SignExtend{regsize}(data); 2026-03-12 12:23:09 2025-09_rel_asl1