[SOLVED] EECS 151/251A Lab 8 : ALU Control and Datapath

1 Objective
The main objectives of this lab are
• Build the basic elements of the MIPS datapath that will eventually be used to build
a complete processor.
2 Pre-requisite
For this lab you are expected to be familiar with MIPS single cycle processor from sections
4.2, 4.3 and 4.4 of the textbook.
3 Data Memory
You will be implementing the memory components, ALU control block, and next PC logic
in this lab. Instruction memory and data memory are the most crucial components since
they are used to store instructions and data respectively. Instructions are read from instruction memory that process data stored in the data memory. Under normal circumstances,
instructions and data are stored in different parts of the same large memory blocks. For
ease in this lab, we will use different memory blocks for data and instructions.
1
Computer Architecture and Design, Lab 8 2
Write a behavioral Verilog code to implement the data memory of size 64 words, where
a word is 32 bits in size. Remember that your code must be synthesizable. A memory
write only commits to the memory on the negative edge of a clock, where read operations
occur on the positive edge of the clock. In addition, memory reads and writes must have
a delay of 20. Be sure to use non-blocking assignments
The data memory must have the following inputs:
Address The 32-bit address where the data is either written or read.
Write Data The 32-bit data that is to be written at the address specified by the Address
input above.
MemRead A single bit signal which should be set when you wish to read data from the
memory.
MemWrite A single bit signal which should be set when you wish to write data to the
memory.
Clock The clock signal to synchronize data writes.
The data memory must have the following outputs:
Read Data The 32-bit data that is read from the address specified by the Address input
when a memory read operation is performed.
Note: MemRead and MemWrite must not be active at the same time.
PAT05F08.eps
Address Read
data
Data
memory
a. Data memory unit
Write
data
MemRead
MemWrite
b. Sign-extension unit
Sign
extend
16 32
Fig. 1: Memory Unit
Your Data memory module must have the port definition.
module DataMemory ( ReadData , Address , WriteData ,
MemoryRead , MemoryWrite , Clock ) ;
Computer Architecture and Design, Lab 8 3
input [ 3 1 : 0 ] Address , WriteData ;
input MemoryRead , MemoryWrite , Clock ;
output [ 3 1 : 0 ] ReadData ;
/∗ w r i t e your code he re ∗/
endmodule
Use the Verilog code DataMemoryTest.v for testing your code.
Demonstrate your program to the TA; .
4 ALU Control
As described in the previous lab, the ALU control block, takes the following 2 as inputs:
• ALUOP(4 bits) from the main control unit
• Function field in an R-type instruction (bits [5:0] of the instruction).
The output of the ALU control unit is a 4-bit signal that directly controls the ALU block.
Use the following form as the module interface:
module ALUControl ( ALUCtrl , ALUop, FuncCode ) ;
input [ 3 : 0 ] ALUop;
input [ 5 : 0 ] FuncCode ;
output ALUCtrl [ 3 : 0 ] ;
/∗ w r i t e your code he re ∗/
endmodule
Note: The ALUop you will use here is different from previous labs. For an R-type
instruction, ALUop should be 1111. For I-type instructions, ALUop should be the value of
ALUCtrl for that instruction. Your output should have a delay of 2.
Write a test bench to test your code with the following cases. Fill in the expected
ALUCtrl for the given inputs before you proceed. Remember that your code must be
synthesizable.
Test Case ALUop FuncCode Expected ALUCtrl
1 0010 XXXXXX
2 0110 XXXXXX
3 1111 000000
4 1111 000010
5 1111 100000
6 1111 100010
7 1111 100100
8 1111 100101
9 1111 101010
Computer Architecture and Design, Lab 8 4
Use $monitor or $display commands to print the inputs (ALUop, FuncCode) and the
output (ALUCtrl) values for each test case. Copy and paste the test result output:
5 Next PC Logic
Write a behavior model for calculating the next PC for an instruction. It will use information from the processor control module and the ALU to determine the destination for the
next PC.
Computer Architecture and Design, Lab 8 5
Use the following module interface:
module NextPClogic (NextPC , CurrentPC , JumpField ,
SignExtImm32 , Branch , ALUZero , Jump ) ;
input [ 3 1 : 0 ] CurrentPC , SignExtImm32 ;
input [ 2 5 : 0 ] JumpField ;
input Branch , ALUZero , Jump ;
output [ 3 1 : 0 ] NextPC ;
/∗ w r i t e your code he re ∗/
endmodule
Where JumpField is the jump field from the current instruction and SignExtImm32 is
the sign extended lower 16 bits of the current instruction. Branch is true if the current
instruction is a branch instruction, Jump is true if the current instruction is a jump, and
ALUZero is the Zero output of the ALU.
Any additions with a constant should have a delay of 1, general addition should have
a delay of 2, and any multiplexers should have a delay of 1 (This includes statements
inside if/else statements). Write a test module to test your module’s correct operation.
In your test code, use $display command to print the inputs (CurrentPC, JumpField,
SignExtImm32, Branch, ALUZero, Jump) and the output (NextPC). Copy and paste the
test result output:
Computer Architecture and Design, Lab 8 6
6 Deliverables
Please turn-in the following:
• Your Verilog code along with the test code for all three components. Ensure that
your program is clearly commented.
• Files with waveform trace from DVE (print to file) when running your testbench for
each of the components. Be sure to set it to require enough pages that the full signal
values are readable in the wavefore trace. Postscript format is fine.