1. Digital Logic
2. Project: Logic Circuit Fundamentals

Introduction

Background

Requirements

1. Configure your Blackboard with a downloaded .bit file, and deduce the logic circuits it contains

Download and decompress the pre-compiled bitstream from the link below. After the decompressed .bit file is available on your computer, open the Hardware Manager from Vivado’s main IDE, autoconnect to the Blackboard, select “Program Device”, and select the .bit you just downloaded. The .bit file will configure your Blackboard with four different circuits that use slide switches as inputs and LEDs for outputs. After your Blackboard is programmed, you can interact with the circuits to deduce their design. and complete the truth tables below to document the behavior. Note you do not need to create a project for this task.

Blackboard_P2.Zip

Circuit 1

The first circuit uses slide switches SW0 and SW1 as inputs and LD0 as an output. Use the switches to apply all four possible input patterns, and record LD0’s response in the table below (note LD0 will illuminate when the circuit’s output is a ‘1’). When the table is complete, click “Check Result”.

SW1	SW0	LD0
0	0
0	1
1	0
1	1
Reset Check Result

Circuit 2

The second circuit uses SW1, SW2 and SW3 as inputs, and LD1 as an output. Probe Circuit 2 the same way you did Circuit 1, complete the truth table below, and check your results.

SW3	SW2	SW1	LD1
0	0	0
0	0	1
0	1	0
0	1	1
1	0	0
1	0	1
1	1	0
1	1	1
Reset Check Result

Circuit 3

The third circuit uses SW4, SW5, SW6, and SW7 as inputs, and LD2 as output. Probe Circuit 3 the same way you did Circuit 1 and 2, complete the truth table below, and check your results.

SW7	SW6	SW5	SW4	LD2
0	0	0	0
0	0	0	1
0	0	1	0
0	0	1	1
0	1	0	0
0	1	0	1
0	1	1	0
0	1	1	1
1	0	0	0
1	0	0	1
1	0	1	0
1	0	1	1
1	1	0	0
1	1	0	1
1	1	1	0
1	1	1	1
Reset Check Result

Create your own duplicate circuits

After you have correctly completed the truth tables, create your own circuits to implement the same behavior as the three circuits you just probed. Create a new Vivado project, and add a new Verilog source file. Define the eight slide switches as inputs, and three LEDs as outputs. Then, based on your truth table results, create Verilog assignment statements (using SOP logic) to drive the three LEDs exactly as they were driven in the downloaded file. Your competed Verilog module will have three assignment statements; the first one is provided, but you must write the other two. Your Verilog should similar to the code below.

module top (
    input [7:0] sw,
    output [2:0] led
);

assign led[0] = (sw[0] & ~sw[1]) | (~sw[0] & sw[1]);
assign led[1] = // you must write this statement
assign led[2] = // and this one too

endmodule

Create a new constraints file, and connect the Verilog “sw” inputs and “led” outputs to the proper pins on the ZYNQ device.

When your Verilog and constraints source files are complete, click “Generate Bitstream” to automatically run all the required implementation steps. (Note: In Vivado, if you execute a process that uses outputs from one or more previous processes, Vivado will automatically check to make sure all previous processes and files are up to date. If any files needed to be updated, Vivado will automatically run any required processes.)

2. Try POS Instead

Modify the source file from requirement 1 above by commenting-out the SOP equations, and then create POS equations to drive the LEDs in exactly the same way. The TA will check your source file to make sure both the SOP and POS versions are present.

3. Circuit 4

Program your Blackboard with the .bit file you downloaded in requirement 1. That .bit file contains a fourth circuit that uses SW3 – SW6 as inputs, and LD3 as an output. Probe this fourth circuit, create a new Verilog source file that behaves identically, program your Blackboard, and verify it performs identically. Create a K-Map or Truth Table when identifying the logic of the circuit, and be prepared to show it when being graded.

4. Create a New Circuit

Design and implement a warning light system that:

1. Illuminates a yellow light whenever any of the following are true:

• Only the Coolant Level is low
• Only the Oil Level is low
• The Oil Temperature is too high and the Oil Level is OK
• The Coolant Temperature is too high and the Oil Level is too low

2. Illuminates a Red light (using the other LED package) whenever any of the following are true:

• The Coolant temperature is too high and the Coolant level is too low
• The Oil Temperature is too high and the Oil Level is too low
• The Coolant and Oil Temperatures are too high at the same time
• The Coolant and Oil levels are too low at the same time that the Coolant Temperature is too high and the Oil Temperature is OK.

Create a Verilog description of a circuit that meets these requirements, and implement the circuit on your Blackboard. Use four slide switches to represent the sensor inputs and use two RGB LEDs for the outputs.

Challenges

1. LED Controller Using Switches