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Verilog tutorial

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.

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Verilog tutorial

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

  2. 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

  3. 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 1364-1995 (Verilog-1995)

  4. 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

  5. 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

  6. 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

  7. Up_counter: combinational ckt • `ifdef WAY_NO1 // 指定D的方法<1> -> 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<2> -> Combinational circuit • reg [7:0]value_now_d; // D values for flip-flops • always@(reset or value_now) // sensitivity list • begin • if(reset) • vaule_now_d=8'd0; • else • value_now_d=value_now+1'b1; • end • `endif

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

  9. Up_counter: max • module UP_COUNTER_max(clock,reset,max,value_now); • input clock,reset,max; • always@(reset 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

  10. Up_counter: freeze • input clock,reset,max,freeze; • always@(reset 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

  11. Up_counter: pre_load • input clock,reset,max,freeze,pre_load; • input [7:0]pre_load_val; • always@(reset 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

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

  13. 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,value_now);

  14. 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; • always@(posedge clock) • begin • #5 • $display("Present valur of the up counter=%d",value_now); • end

  15. The outputs/responses • # Present valur of the up counter= x • # Present valur of the up counter= 0 • # Present valur of the up counter= 0 • # Present valur of the up counter= 0 • # 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

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

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

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

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

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

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

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

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

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

  25. Synthesis • Design compiler, Synopsys Inc.

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

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

  28. Recommended books (2) For CAD designer CS students

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