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Simple ALU (Part 2: Instruction Set Implementation)			[TOC]
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---- VIDEO ------------------------------
https://www.youtube.com/embed/0wI4i2qYZ3c
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Description of the Instruction Set
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All instructions are 16-bit patterns and have a simple format. The format can be
described by grouping the bits by four and denoting them, from left to right,
as `Op`, `X`, `Y` and `Z`. For example

---- LATEX ---------------------------------------------------------------------
\text{0001001000110100} \leadsto \text{0001 0010 0011 0100} \leadsto
\text{Op} = \text{0001}, \text{X} = \text{0010}, \text{Y} = \text{0011},
\text{Z} = \text{0100}.
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The bit pattern `Op` is the __opcode__ of the instruction. It specifies the
type of instruction. Because the opcode is a 4-bit pattern we have (only) 16
types of instructions, and the remaining bits are used as operands.  The
instruction set of the ALU can be described as follows:

---- LATEX ---------------------------------------------------------------------
\begin{array}{ll}
\text{Op}   & \text{Effect} \\
0x0   & u(\text{XY}) \to u(\text{%}Z) \\
0x1   & \bigl(u(\text{%}Z)\cdot 2^8 + u(\text{XY})\bigr) \bmod 2^{16} \to u(\text{%}Z) \\
0x2   & \bigl( u(\text{%}X) + u(\text{%}Y)\bigr) \bmod 2^{16} \to u(\text{%}Z) \\
0x3   & \bigl(-u(\text{%}X) + u(\text{%}Y)\bigr) \bmod 2^{16} \to u(\text{%}Z) \\
\end{array}
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Assignment
==========

Add the following instructions to the ALU:

---- LATEX ---------------------------------------------------------------------
\begin{array}{ll}
\text{Op}   & \text{Effect} \\
0x4   & s(\text{XY}) \to s(\text{%}Z) \\
0x5   & \bigl( u(X) + u(\text{%}Y)\bigr) \bmod 2^{16} \to u(\text{%}Z) \\
\end{array}
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:links:	opcode  -> https://en.wikipedia.org/wiki/Opcode