3.3.8.4 W Registers and Byte Mode Instructions

Byte instructions that target the W register array affect only the Least Significant Byte (LSB) of the target register, while word instructions that target the W register array affect only the Least Significant Word (LSW) or the bottom 16 bits of the target register. Since the Working registers are not memory-mapped, only the LSB and LSW of these registers are accessible through byte mode and word mode instructions, respectively, using Register Direct Addressing only.