Lab 2: Objectives For Reviewing T

Lab 2lab Objectivesthe Objective For This Lab Is To Review The Motorol

The objective for this lab is to review the Motorola assembly language instruction set using digital logic gates. This lab will also serve as a review of digital logic and introduce the concept of coding logic designs in assembly.

In this lab, you will overview the assembly logic instructions that can be used for logic gates. A logic gate is an idealized or physical device implementing a Boolean function, performing logical operations on inputs to produce outputs. You will then use these logic gates to create logic circuits in assembly language.

Paper For Above instruction

This paper presents a comprehensive overview of designing and programming basic digital logic gates using Motorola assembly language, integrating fundamental principles of digital logic with low-level programming techniques. The objective is to demonstrate how logical operations—such as NOT, AND, OR, and XOR—can be implemented at the assembly level, fostering a deeper understanding of both Boolean algebra and microcontroller programming.

Digital logic gates are the building blocks of digital systems and serve as the foundation for complex logical and computational functions. Implementing these gates in assembly language requires a thorough understanding of the instruction set and memory management of the Motorola microcontroller. This paper elucidates the steps involved in coding and testing individual logic gates and discusses the subsequent use of these gates in more advanced combinational logic circuits such as Sum-of-Products (SoP) and Product-of-Sums (PoS) expressions.

The programming task involves coding six different logic functions, each demonstrating specific logical operations. For parts 1 through 4, the code must be stored in the EEPROM and executed as permanent read-only memory (ROM). Parts 5 and 6, which involve more complex Boolean simplifications, should be stored in RAM's program section. Additionally, data variables are stored in the RAM data section, facilitating variable manipulation during program execution.

Implementation of Basic Logic Gates in Assembly

1. NOT Gate

The NOT gate inverts the input digital signal; if the input is high (logic 1), the output should be low (logic 0), and vice versa. Implementing the NOT gate involves using the COMA instruction, which complements the accumulator's bits, or the COMB instruction if multiple registers are involved. The BCLR instruction can also be employed to clear a specific bit, effectively setting the output to zero based on input conditions. The assembly code reads an input variable, applies complement operations, and writes the result to the output port, demonstrating the logical negation effectively.

2. 3-Input AND Gate

The AND gate outputs high only when all inputs are high. Using the ANDA or ANDB instruction, the assembly code reads three input variables, performs bitwise AND operations, and stores the resulting logical AND in the output variable. Proper synchronization and sequencing ensure that the logic accurately reflects the Boolean AND operation across all three inputs.

3. 3-Input OR Gate

The OR gate outputs high if at least one input is high. The ORAA or ORAB instructions in assembly are employed to combine the three input variables logically. The code ensures that if any of the inputs are high, the output register is set high, implementing the OR logic correctly.

4. 2-Input XOR Gate

The XOR gate outputs high only when the inputs differ. Using the EORA or EORB instructions, the assembly code reads two input variables and performs a bitwise exclusive OR, enabling the recognition of input differences, which is critical in many digital applications such as parity checks and adders.

Design of Boolean Functions and Logic Circuits

5. Sum-of-Products (SoP)

The SoP form represents a Boolean function as a sum (OR) of product (AND) terms. The process involves analyzing the truth table, deriving the minimal logical expression using Karnaugh maps (K-maps), and translating this expression into assembly instructions. The mapped Boolean function is then coded using assembly instructions to realize the corresponding logic circuit. This approach demonstrates how software can mimic hardware logic gate behavior, facilitating flexible and programmable circuit design.

6. Product-of-Sums (PoS)

The PoS form expresses the Boolean function as a product (AND) of sum (OR) terms. Similar to the SoP process, the truth table is analyzed using K-maps to derive the minimal expression. This expression is then implemented in assembly, providing an alternative formulation of the function, often optimized for different hardware configurations or specific application needs.

Concluding Remarks

Programming low-level assembly instructions for fundamental digital logic gates not only consolidates understanding of Boolean algebra but also enhances proficiency in microcontroller programming. Combining these two skill sets enables the design of more sophisticated digital systems, from simple gates to complex logic circuits. The insights gained through this lab provide a foundation for developing optimized, efficient low-level code that interfaces seamlessly with digital hardware components, paving the way for advanced digital system design and implementation.

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