Description
Total Points: 20 As with previous homeworks, this homework requires using Verilog. A reminder of some important documents (all available on Canvas): 1. Follow the instructions on ModelSim Setup Tutorial to get your environment setup. 2. Read the Command-line Verilog Simulation Tutorial. Additional references are on Canvas under “Verilog Resources” on the main page. 3. Read the Verilog Cheat sheet and Verilog rules pages. Everything you need to know about Verilog are in these documents. 4. Read the Verilog file naming conventions page and adhere to those conventions. Additional information including a link to the script you can use to make sure your files adhere to these rules are on Canvas, directly under the file naming conventions page. 5. Read the Verilog rules checking page on Canvas and adhere to the conventions. This page also provides information on how you can check that your files conform to these rules. You should simulate your solutions both to verify the correct function of your designs for yourself. You also have to hand in a copy of the Verilog files (or submit one per group and update partners.txt accordingly), as mentioned above. Before starting to write any Verilog for each problem, you should do the following: 1. Break down your design into sub-modules. 2. Define interfaces between these modules. 3. Draw schematics (either by hand, or on a computer) for these modules (these will be handed in as scanned schematic.pdf file). 4. Then start writing Verilog. Problem 1 [10 points] Using Verilog, design an 8 -by -16- bit register file (i.e., 8 registers, each of size 16 bits). See the Verilog interface below. It has one write port, two read ports, three register select inputs (two for read and one for write,) a write enable, a reset and a clock input. All register state changes occur on the rising edge of the clock. Your basic building block must be the D-flipflop given in the provided files. The read ports should be all combinational logic. Do not use tri-state logic in your design. Design this register file such that changing the width to 32-bit or 64-bit is straightforward The read and write data ports are 16 bits each. The select inputs (read and write) are 3 bits each. When the write enable is asserted (high) the selected register will be written with the data from the write port. The write occurs on the next rising clock edge; write data cannot flow through to a read port during the same cycle. There is no read enable; data from the selected registers will always appear on to the corresponding read ports. The reset signal is synchronous and when asserted (active high), resets all the register values to 0. The err output should be set to 1 if any register (or other sub-module) in the register file has an error. For now, you may assume that an error only happens in a register if the input or enable is an unknown value, and in other sub-modules if the input is an unknown value. Otherwise it should be set to 0. You must use a hierarchical design. Design a 16-bit register first, and then put 8 of them together with additional logic to build the register file. Do not make any changes to the provided rf_hier.v file. Testbench instructions You must verify your design using the testbench in the supplied tar file and on Github Classroom (of course you are welcome and encouraged to write additional tests on your own). Run the testbench in your hw5_1 directory using the command: wsrun.pl rf_bench *.v The testbench for this problem (rf_bench.v) generates a random set of input signals to your module in each cycle, and compares outputs from your module with outputs that are expected from a perfect register file implementation. If there are no errors in your design you will see a “TEST PASSED” message. If the testbench failed with a “TEST FAILED” message, look for error messages like “ERRORCHECK: Incorrect read data in cycle ” in the testbench output. Above each of these error messages you will see the inputs to your module, your outputs and the expected outputs for that cycle which can help you debug. Verify the design using the testbench in the supplied tar file and on Github Classroom. Problem 2 [10 points] In Verilog, create a register file that includes internal bypassing so that results written in one cycle can be read during the same cycle. Do this by writing an outer “wrapper” module that instantiates your existing (unchanged) register file module; your new module will just add the bypass logic. The list of inputs and outputs of the outer module should be the same as that of the inner module. Do not make any changes to the provided rf_hier.v file. Testbench instructions You must verify your design using the testbench in the supplied tar file and on Github Classroom (of course you are welcome and encouraged to write additional tests on your own). Run the testbench in your hw5_2 directory using the command: wsrun.pl rf_bypass_hier_bench *.v The testbench for this problem (rf_bypass_hier_bench.v) generates a random set of input signals to your module in each cycle, and compares outputs from your module with outputs that are expected from a perfect register file bypass implementation. If there are no errors in your design, you will see a “TEST PASSED” message. If the testbench failed with a “TEST FAILED WITH xx ERRORS” message, look for error messages like “ERRORCHECK: Read data incorrect in cycle ” in the testbench output. Above each of these error messages you will see the inputs to your module, your outputs and the expected outputs for that cycle which can help you debug.
