Store Register Byte (unprivileged).
Is the 32-bit name of the general-purpose register to be transferred.
Is the 64-bit name of the general-purpose base register or stack pointer.
Is the optional signed immediate byte offset, in the range -256 to 255, defaulting to 0.
Store Register Byte (unprivileged) stores a byte from an address in memory and zero-extends it. The address used for the store is calculated from a base register and an immediate offset. When executed at EL1, the memory access is restricted as if execution was at EL0. Otherwise, the access permission is for the Exception level at which the instruction is executed. For information about memory accesses see Load/Store addressing modes in the ARMv8-A Architecture Reference Manual.