4.3.8.4 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 affects 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.