3.3.11.1 Byte to Word Conversion
The dsPIC33A CPU has two instructions that are helpful when mixing 8-bit and 16-bit ALU operations.
The Sign-Extend (SE) instruction takes a byte value in a W register or data memory and creates a sign-extended word value that is stored in a W register.
The Zero-Extend (ZE) instruction clears the 8 MSbs of a word value in a W register or data memory and places the result in a destination W register.