SB

SB : Store Byte (and update the pointer)

Data : This instruction inserts one byte (8 bits) in the destination register, emulating the "Store Byte" instruction of Load-Store architectures. The source data (either

a 4-bit immediate value (short immediate or extended immediate forms)
a register (si4) (short register or extended register forms) or
a 16-bit value (long immediate form)

) is truncated (only the 8 lower bits are kept) then shifted left, according to the Least Significant Bit(s) of the eventual associated Address register. Then the result is inserted in the word of the destination register.

Address : If the source register is not a Data register, then the offset is zero. If the source is a Data register, the 2 LSBs (or only one for YASEP16) of the corresponding Address register are used as offset, and this Address register is updated with this offset (incremented or decremented).

Note : this instruction was meant to use auxiliary data from other registers. As of 2009-07, in order to use the auto-update function, the extended form (32-bit instruction) must be used.