26.2.1. Execution in terms of Micro Instructions

So, basically what we can do is that, we can actually write a micro routines which can be shared. For example, as I told you like add and sub. So, most of the case will be similar excepting 1 bit position or the 1 control signal corresponding to add or subtract of the ALU.

In this chunk, we learn that micro routines can be created to handle similar operations like addition and subtraction efficiently. The key idea is that most of the steps involved in both operations are alike, differing only in a specific control signal that dictates whether to add or subtract. This means instead of writing separate instructions for each operation, we can use one shared routine with slight variations.

Consider micro routines like shared recipes that can be slightly adjusted to make either a chocolate cake or a vanilla cake. The fundamental steps (mixing, baking, etc.) are the same, but the only change is the flavoring ingredient. This efficiency allows chefs (like micro routines) to save time and resources while still producing delicious results.

So, as I told you in the last class that in this unit we will also see how a complete macro instruction is executed in terms of micro instructions.

Here, the focus shifts to executing a complete macro instruction using micro instructions. A macro instruction is a higher-level operation, whereas micro instructions are the lower-level steps needed to perform it. This chunk highlights the importance of understanding how these two levels of instructions work together.

Think of a macro instruction as a full recipe for a dinner, while micro instructions are the individual cooking steps. Just as you need to follow each step (preparation, cooking time, etc.) in the recipe to achieve the final dish, each micro instruction must be executed correctly to fulfill the macro instruction.

We are going to show you how a complete macro instruction is executed in terms of micro instruction, and we were going to take the help of jump on zero 𝑀 (𝐽𝑀𝑃𝑍 𝑀).

In this literature, an example instruction, 'jump on zero (JMPZ)', is introduced. It's a macro instruction that dictates the program's flow based on whether a condition (the zero flag) is met. This example serves as a practical illustration of how macro instructions translate into micro instructions.

Imagine playing a video game where you only move to a special location when your character's health is zero. The 'jump on zero' instruction is similar—you make a 'move' (execute a routine) only when certain conditions are satisfied, just like waiting for a health indicator to trigger your next action.

If I say that I will have a similar macro program micro program for different type of macro instructions which are common in type and then you will jump from the main micro program and again come and execute the different part.

This segment discusses how branching works within micro programs. It underscores that when using shared routines for different macro instructions, there might be multiple jumps back and forth within the micro program, termed as implicit jumps. This branching allows the program to handle multiple scenarios efficiently using a single routine.

Imagine a public transportation system that has a common route for several buses. Depending on the passenger's destination (like different macro instructions), the bus may need to make various stops (jump instructions). This approach helps save time and resources while ensuring that everyone reaches their desired location.

There are basically 2 parts. One is called the explicit because of the instruction type if it is add, sub this will not be there, and there will be some implicit type which will be coming in to the micro routines because you are doing an optimization.

This segment differentiates between explicit and implicit jumps in micro instruction sequences. An explicit jump is when a specific instruction in the macro program requires a direct action (e.g., jumping to another memory location). Conversely, implicit jumps are the underlying corrections or adjustments to the flow of the micro routine made for optimization.

Think of a traffic system where some intersections (explicit jumps) are planned and signposted for vehicles (car drivers) to jump lanes or paths based on certain signals (instructions). In contrast, there may be backroads or shortcuts (implicit jumps) that drivers can take to streamline their journey without explicit direction.

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