CSE12-02 Lab 2: Higher Order Logic Solution

Minimum Submission Requirements
● Ensure that you upload the following files for your Lab2 Gradescope submission with the file names exactly as shown:
○ lab2_part1.dig
○ lab2_part2.dig
○ lab2_part3.dig
Objective
The objective of this lab is to build higher order logic structure and introduce an overly simple data path.
Breakdown
This assignment consists of three parts:
Part-1: Single ALU Operation ->complete lab2_part1.dig
Part-2: Display Decimal from 2's Complement ->complete lab2_part2.dig
Part-3: Data Path ->complete lab2_part3.dig
External Resources
Registers, Flip-Flops, and Modular Design This short video provides a very brief introduction to storage elements in digital logic. We will be utilizing their principles in lab2. If by now, storage elements have not yet been covered in lecture, this quick video will give you a primer in this subject. After watching this video, please go through this note on registers to ensure you have the working knowledge of storage elements needed for lab 2.
Lab Demos
Tests
Specifications: Part-1
Part-1: Description
In this part of the lab you will build a single operation ALU. This ALU will implement a Bitwise left Rotation. For this lab assignment you are not allowed to use Digital's Arithmetic components.
IF YOU ARE FOUND USING THEM, YOU WILL RECEIVE A ZERO FOR LAB2!
The ALU you will be implementing consists of two 4-bit inputs (named inA and inB) and one 4-bit output (named out). Your ALU must rotate the bits in inA by the amount given by inB (0-15).
Part-1: User Interface
You are provided an interface file lab2_part1.dig; start Part-1 from this file. You are not permitted to edit the content inside the dotted lines rectangle.

Figure: lab2_part1.dig Interface
Part-1: Example
When you open the lab2_part1.dig file, you will of course not see these exact values in green because that is what we used to verify your circuit correctly working by clicking on the Simulate button. On your end, you should go through all possible test cases to verify your design works. Make sure to name all the wires and input/outputs correctly so that they match the test interface names within lab2_part1.dig. You will need to do the same for part2 and part 3 as well.
Hint: Using Multiplexers will help you out a lot here.
To help you make sure you are testing your rotation results left, you can try using the included rotate.cpp C++ program for verification. Modify the values of the array arr elements and the rotation value rotateBy. If you don’t have a C++ compiler on your local machine, try running the code in onlinegdb.
The “Tunnel” component in Digital for Lab2
In Lab1, you might have noticed how much effort it took to draw so many inputs and wire them all over the place without unintentionally connecting them to the incorrect outputs and nodes! Turns out, Digital does provide some means to help reduce this burden.
This manifests as the Tunnel component. Go to Components->Wires->Tunnel. The symbol looks like a triangle with one vertex being a dot. The idea is that instead of extending your wires physically all over your circuit drawing space by drawing them as lines, you can use tunnels as placeholders in different locations on your diagram for the same wire. These tunnels must have the same name so as to symbolize the same electrical connection. You can rotate the tunnel, to align it like any other symbol with the ‘r’ hot key. See the Digital Cheat Sheet under Pages for more hints.
You are provided the file playWithTunnels.dig to give you an idea of how tunnels work in Digital. Think of them as being like wormholes that can connect 2 physically separate points on your circuit diagram through the same wire connection.

Figure: playWithTunnels.dig screenshot
Note that all the Interface areas in the .dig files for part1, part2 and part3 have tunnel components in them. That means when you draw your circuit outside the interface box in these files, you will need to draw the appropriate number of tunnel wires which hook up (via wormholes!) to the provided inputs and outputs within the interface box. Make sure the tunnels have the correct wire names.
Specifications: Part-2
Part-2: Description
In this part of the lab, we will illuminate two 7-segment displays. You will need to understand 2's Complement to determine when the input 4-bit binary number corresponds to a negative or positive number. To understand how an LED display works in Digital, please refer to the playWithLED_Display.dig file provided. You should play with different input combinations to see how it influences the LED Display value. In the screenshot below, note how I was able to generate the display of “3” on the Hex display by lighting up only certain input wires to the unit.

Figure: playWithLED_Display.dig screenshot
Here is a picture of how the different segments light up to produce the different displays:

Figure: Lighting up dif erent segments to produce display of 0-8
Note in the picture above that we showed displays only from 0-8 since in 4-bit 2s complement representation, 8 is the largest modulus value you can represent (the range of integers would be -8 to +7).
Your circuit in Part-2 must accept a 4-bit 2's complement input {in3, in2, in1, in0} where in3 is the most significant bit and in0 is the least significant bit. The outputs of your circuit must illuminate the two 7-segment displays such that they display the decimal value of the input. Since this a 4-bit 2s complement represented number, that means the range of numbers (24=16) that can be shown correctly on the hex display (with sign) is [-24-1, +24-1-1] = [-8, +7]
Part-2: User Interface
You are provided an interface file lab2_part2.dig, start Part-2 from this file. You are not permitted to edit the content inside the dotted lines rectangle.

Figure: lab2_part2.dig Interface
Part-2: Example
In the figure above, the input is {in3, in2, in1, in0} = {0, 0, 1, 1} Which means the input signal in, as a bus, reads
0011. Which is the 2's complement binary representation of the value +3. Note: only the middle segment, sign_g, (it appears as signg on the Digital screenshot) on the left display will be illuminated, and that too ONLY for negative
values. Since +3 is a positive number, it is not illuminated in the above example. All the remaining sign signals remain turned off for both positive and negative numbers.
Specifications: Part-3
Part-3: Description
In this part of the lab, you will create a data path for the ALU you build in Part-1. This data path will consist of 4
registers.
In this lab, we are using the register components. Refer to playwithRegister.dig to get a good starting idea of how this component works.
You will need to address 1 register via the interface select signals to determine which 4-bit register to write the input value to. Then using the D-Flip-flops in Digital.
You will use only one Clock Input to keep the circuit synchronized. That is, with Clock=0, set up your register write values. Once the values are set up, set Clock to 1. For this lab, a manual setting of clock signal from 0 to 1 is needed. Do not create a periodic clock signal.
Part-3: User Interface
You are provided an interface file lab2_part3.dig, start Part-3 from this file. You are not permitted to edit the content inside the dotted lines rectangles.
Figure: lab2_part3.dig Interface
Part-3: Example
In this design, the user can choose out of the 4 registers where to store the 4-bit value which needs to be rotated (inA from part-1) and also which register to store the rotation amount (inB from part-1), using the selwrite register selection inputs. The user ensures they direct these two registers to the correct Register Selection: Read From values for inA and inB inputs values to the ALU.
In the figure above, we have written the value 5 to Register 3 and the value 1 to Register 1. Then, we read from
Register 3 the value 5 to ALU input A and read from Register 1 the value 1 to ALU input B. Rotating 5 left by 1 b it results in {1, 0, 1, 0} displayed in the ALU Output as hexadecimal A.
Grading Rubric (total 100 points)
30 pt Part-1 completed
30 pt Part-2 completed
40 pt Part-3 completed