This addressing mode requires one word of extension.
The operand is in a memory location referenced by an effective
address computed by adding together the contents of the program
counter, a second data or address register, and an 8-bit displacement.
The value in the second register can either be a full long word or a sign-
extended word value. This is specified by a .W or .L extension after
the register. If no extension is used, the assembler assumes a word