Verilog tutorial Hong-Hui Chen 05/17/2002 VLSI Design Course

Outline What is Verilog? Register transfer level (RTL) Up_counter example Test_bench for Up_counter Get a simulator Simulation and verification Synthesis Back end flow and a real CHIP Recommended books

What is Verilog Verilog is first introduced in 1984 for Gateway Verilog-XL digital simulator In 1989, Gateway acquired by Cadence. Then in 1990, Cadence release the Verilog language and Verilog PLI to public. Open Verilog International(OVI) was formed to maintain the Verilog standard, in 1993, OVI releases the Verilog 2.0 Reference Manual, then becomes the IEEE (Verilog-1995)

Register transfer level (RTL) Elements with memorial ability -> flip-flops -> sequential circuit Combinational circuit is used to calculate the next state of the flip-flops

Up_counter example Four sample designs for up_counter: up_counter_hello_world.v up_counter_max.v up_counter_max_freeze.v up_counter_max_freeze_pre_load.v

Up_counter: in out declaration module UP_COUNTER_hello_world(clock,reset,value_now); input clock,reset; output [7:0]value_now; reg [7:0]value_now; // Q value for filp-flops …… endmodule

Up_counter: combinational ckt `ifdef WAY_NO1 // 指定 D 的方法 -> Combinational circuit wire [7:0]value_now_d; // D values for flip-flops assign value_now_d=reset?8'b0:(value_now+1'b1); `else // 指定 D 的方法 -> Combinational circuit reg [7:0]value_now_d; // D values for flip-flops or value_now) // sensitivity list begin if(reset) vaule_now_d=8'd0; else value_now_d=value_now+1'b1; end `endif

Up_counter: sequential ckt A edge triggered always block will infer real flip-flops clock) begin value_now<= value_now_d; end Above statement will use 8 flip-flops

Up_counter: max module UP_COUNTER_max(clock,reset,max,value_now); input clock,reset,max; or value_now or max) begin if(reset) value_now_d=8'd0; else if(max) value_now_d=8'd255; else value_now_d=value_now+1'b1; end

Up_counter: freeze input clock,reset,max,freeze; or value_now or max or freeze) begin if(reset) value_now_d=8'd0; else if(freeze) value_now_d=value_now; // 把 Q 又 assign 給 D else if(max) value_now_d=8'd255; else value_now_d=value_now+1'b1; end

Up_counter: pre_load input clock,reset,max,freeze,pre_load; input [7:0]pre_load_val; or value_now or max or freeze or pre_load or pre_load_val) begin if(reset) value_now_d=8'd0; else if(freeze) value_now_d=value_now; // 把 Q 又 assign 給 D else if(max) value_now_d=8'd255; else if(pre_load) value_now_d=pre_load_val; else value_now_d=value_now+1'b1; end

Test_bench for Up_counter How can we ensure our design is right?

Test_bench for Up_counter (1) `timescale 1ns/1ps module test_up_counter; // test bench module reg clock,reset,max,freeze,pre_load; reg [7:0]pre_load_val; wire [7:0]value_now; UP_COUNTER_max_freeze_pre_load MY_COUNTER(clock,reset,max,freeze,pre_load,pre_load_val,val ue_now);

Test_bench for Up_counter (2) initial begin clock=1; reset=1; max=0; freeze=0; pre_load=0; pre_load_val=0; #81 reset=0; end always #10 clock=~clock; clock) begin #5 $display("Present valur of the up counter=%d",value_now); end

The outputs/responses # Present valur of the up counter= x # Present valur of the up counter= 0 # Present valur of the up counter= 1 # Present valur of the up counter= 2 # Present valur of the up counter= 3 # Present valur of the up counter= 4

Get a simulator (1) Go to the web as figure at right side Register a new account

Get a simulator (2) Put “ Download ISE WebPACK ” button ID and password required Select “ Custom ” download configuration

Get a simulator (3) Select “ MXE Simulator ” only -> Download -> Install In the installation course, It will remind you to get a license!

Get a simulator (4) Fill the form and submit!

Get a simulator (5) Please setup the license correctly!

Simulation and verification (1) File -> New -> Project Copy: 1) Test_up_counter.v 2) Up_counter_max_freeze_pre_load.v to

Simulation and verification (2) Design -> Compile Select all the sources Compile them!

Simulation and verification (3) Design -> Load Design … Select the test bench module

Simulation and verification (4) Execute run 10000ns -> Simulation result is outputted to screen cause $dsiplay() is used in the test bench!

Synthesis Design compiler, Synopsys Inc.

Back end flow and a real CHIP Automatic routing, cell placement, timing analysis CHIP photo!

Recommended books (1) Synthesis issues Beginner’s choice Chinese copy available Advanced book Chinese copy available

Recommended books (2) For CAD designer CS students