Computer-Organization HOMEWORK 5- RISC-V CPU Solution

Overview
The goal of this homework is to help you understand how a RISC-V work and how to use Verilog hardware description language (Verilog HDL) to model electronic systems. In this homework, you need to implement ALU and decoder module and make your codes be able to execute 17 RISC-V instructions. You need to follow the instruction table in this homework and satisfy all the homework requirements. In addition, you need to verify your CPU by using Modelsim. General rules for deliverables
 You need to complete this homework INDIVIDUALLY. You can discuss the homework with other students, but you need to do the homework by yourself. You should not copy anything from someone else, and you should not distribute your homework to someone else. If you violate any of these rules, you will get NEGATIVE scores, or even fail this course directly
 When submitting your homework, compress all files into a single zip file, and upload the compressed file to Moodle.
Please follow the file hierarchy shown in Figure 1. F740XXXXX ( your id ) (folder) src ( folder ) * Store your source code report.docx ( project report. The report template is already included. Follow the template to complete the report. )

Figure 1. File hierarchy for homework submission
 You should finish all the requirements (shown below) in this homework and
Project report.
 Verilog and SystemVerilog generators aren’t allowed in this course.
Instruction format:
The highlighted instructions that have been completed in the previous job.
 R-type
31 25 24 20 19 15 14 12 11 7 6 0
funct7 rs2 rs1 funct3 rd opcode Mnemonic Description
0000000 rs2 rs1 000 rd 0110011 ADD rd = rs1 + rs2
0100000 rs2 rs1 000 rd 0110011 SUB rd = rs1 - rs2
0000000 rs2 rs1 100 rd 0110011 XOR rd = rs1 ^ rs2
0000000 rs2 rs1 110 rd 0110011 OR rd = rs1 | rs2
0000000 rs2 rs1 111 rd 0110011 AND rd = rs1 & rs2
 I-type
31 20 19 15 14 12 11 7 6 0
imm[11:0] rs1 funct3 rd opcode Mnemonic Description
imm[11:0] rs1 010 rd 0000011 LW rd = M[rs1 + imm]
imm[11:0] rs1 000 rd 0010011 ADDI rd = rs1 + imm
imm[11:0] rs1 100 rd 0010011 XORI rd = rs1 ^ imm
imm[11:0] rs1 110 rd 0010011 ORI rd = rs1 | imm
imm[11:0] rs1 111 rd 0010011 ANDI rd = rs1 & imm
imm[11:0] rs1 000 rd 1100111 JALR rd = PC + 4
PC = imm + rs1
(Set LSB of PC to 0)
 S-type
31 25 24 20 19 15 14 12 11 7 6 0
imm[11:5] rs2 rs1 funct3 imm[4:0] opcode Mnemonic Description
imm[11:5] rs2 rs1 010 imm[4:0] 0100011 SW M[rs1 + imm] = rs2
 B-type
31 25 24 20 19 15 14 12 11 7 6 0
imm[12|10:5] rs2 rs1 funct3 imm[4:1|11] opcode Mnemonic Description
imm[12|10:5] rs2 rs1 000 imm[4:1|11] 1100011 BEQ PC = (rs1 == rs2) ?
PC + imm : PC + 4
imm[12|10:5] rs2 rs1 001 imm[4:1|11] 1100011 BNE PC = (rs1 != rs2) ?
PC + imm : PC + 4
 U-type
31 12 11 7 6 0
imm[31:12] rd opcode Mnemonic Description
imm[31:12] rd 0010111 AUIPC rd = PC + imm
imm[31:12] rd 0110111 LUI rd = imm
 J-type
31 12 11 7 6 0
imm[20|10:1|11|19:12] rd opcode Mnemonic Description
imm[20|10:1|11|19:12] rd 1101111 JAL rd = PC + 4
PC = PC + imm
Homework Description
Module
a. top_tb module
b. “top_tb” is not a part of CPU, it is a file that controls all the program and verify the correctness of our CPU. The main features are as follows: send periodical signal CLK to CPU, set the initial value of IM, print the value of DM, end the program.
※You do not need to modify this module.
c. top module
“top” is the outmost module. It is responsible for connecting wires between CPU, IM and DM.
Here are the wires:
 instr_read represents the signal whether the instruction should be read in IM.
 instr_addr represents the instruction address in IM.
 instr_out represents the instruction send from IM .
 data_read represents the signal whether the data should be read in DM.
 data_write has four signal , and every signal represents the byte of the data whether should be wrote in DM.
Mem[0] =
{Mem[0][31:24],Mem[0][23:16],Mem[0][15:8],Mem[0][7:0]} data_write[3] => control Mem[0][31:24] data_write[2] => control Mem[0][23:16] data_write[1] => control Mem[0][15:8 ] data_write[0] => control Mem[0][7:0 ]
 data_addr represents the data address in DM.
 data_in represents the data which will be wrote into DM .
 data_out represents the data send from DM . ※You do not need to modify this module.
d. SRAM module
“SRAM” is the abbreviation of “Instruction Memory” (or “Data Memory”). This module saves all the instructions (or data) and send instruction (or data) to CPU according to request.
※You do not need to modify this module
e. CPU module
“CPU” is responsible for connecting wires between modules, please add your code to complete this module ※You should modify this module.
 Reference Block Diagram

 Register File
Register ABI Name Description Saver
x0 x1 x2 x3 x4 x5
x6 – 7 x8 x9
x10 - 11 x12 - 17 x18 - 27 x28 - 31 zero ra
sp
gp tp t0
t1 - 2 s0/fp s1
a0 - 1 a2 - 7
s2 - 11 t3 - 6 Hard-wired zero
Return address
Stack pointer
Global pointer
Thread pointer
Temporary / alternate link register
Temporaries
Saved register / frame pointer
Saved register
Function arguments / return values
Function arguments
Saved registers
Temporaties --Caller
Callee
---
--Caller
Caller
Callee
Callee
Caller
Caller
Callee
Caller
 Test Instruction

 .text: Store instruction code.
 .init & .fini: Store instruction code for entering & leaving the process.
 .rodata: Store constant global variable.
 .bss & .sbss: Store uninitiated global variable or global variable initiated as zero.
 .data & .sdata: Store global variable initiated as non-zero .stack: Store local variables
b. main.S
This will verify RISC-V instructions above (17 instructions).
c. main0.hex & main1.hex & main2.hex & main3.hex
Using the cross compiler of RISC-V to compile test program, and write result in verilog format. So you do not need to compile above program again.
Homework Requirements
1. Complete the CPU that can execute 17 instructions from the RISC-V ISA section.
2. Verify your CPU with the benchmark and take a snapshot (e.g. Figure 3)

Figure 3. Snapshot of correct simulation
a. You can verify the execution results by checking waveforms.
3. Finish the Project Report.
a. Complete the project report. The report template is provided “report.docx”.
Important
When you upload your file, please make sure you have satisfied all the homework requirements, including the File hierarchy, Requirement file and Report format.
If you have any questions, please contact us.
Score
Your score is divided into two parts:
b. Report (25%): You should take a screenshot of your result, and write your report in “report.docx”.