Synopsys Tutorial: Power Estimation

Power Estimation with OSU Standard Cell Library and Synopsys tools (PrimeTime-Px By Syed Haider 1. Starting Fresh: Download Oklahoma State University Library from http://vcag.ecen.okstate.edu/projects/scells/ Specifically, from: http://vcag.ecen.okstate.edu/projects/scells/download/iit_stdcells_v2.3beta/ Download the iitcells_lib_2.3.tar.gz package. 2. untar the library somewhere nice like your home directory where you will really never touch it (i.e. /home/syedh/). The Directory will be called iit_stdcells. 3. Create a project directory somewhere else. (example: mkdir /home/syedh/Project1) In Project1 create another directory called WORK. 4. Back in Project1 directory create an empty file called: .synopsys_dc.setup This file will specify to Synopsys and design_vision software what libraries you are using. A sample version of the file is listed below. The path after “/home/syedh/” should remain unchanged if this tutorial is being followed correctly!!! # .synopsys_dc.setup file # Define the target tehcnology library, symbol library, # and link libraries set target_library /home/syedh/iit_stdcells/lib/tsmc018/lib/iit018_stdcells.db #do not have a symbol library #set symbol_library #set link library (set as same as target library) set link_library “/home/syedh/iit_stdcells/lib/tsmc018/lib/iit018_stdcells.db *” set designer "Your Name" 5. Copy /home/syedh/iit_stdcells/lib/tsmc018/lib/iit018_stdcells.v into Project1 Directory. 6. Now it is design time. Create verilog description of something amazing. Here is a design of a full adder and some registers that spans multiple design files (full_adder.v, top.v): //full_adder.v //This is a module for a 1 bit Full Adder module full_adder(a,b, c_in, s, c_out); input a, b, c_in; output wire s, c_out; assign s = a ^ b ^ c_in; assign c_out = ((a & b)) | (c_in & (a^b)); endmodule //////////////////////////////////////////////////////////////////////////////// //top.v //This contains a full adder with some registers for input and output. `timescale 1ns/10ps module top (clk, a, b, c_in, sum, c_out); input clk, a, b, c_in; output sum, c_out; reg in_a; reg in_b; reg sum_reg; reg c_out_reg; reg c_in_reg; full_adder fa1(.a(in_a), .b(in_b), .c_in(c_in_reg), .s(sum), .c_out(c_out)); always @(posedge clk) begin in_a = a; in_b = b; c_in_reg = c_in; c_out_reg = c_out; sum_reg = sum; end endmodule 7. Now it is time to create a test bench file to test the design. The things that will be highlighted in purple are system tasks that will create dumps (value change dumps) of signals in your design. //tb_top.v //testbench `timescale 1ns/10ps module tb_top(); reg clk; reg a, b, c_in; wire c_out, sum; //clocking description initial begin clk = 0; end //clock period is #100 always begin #50 clk = ~clk; end //initialize input to full adder initial begin a = 0; b = 0; c_in = 0; end /////////////////////////////// // Toggle the inputs at varying rates /////////////////////////////// //toggle carry_in initial begin #60; repeat (50) begin c_in <= ~c_in; #100; end end //toggle a initial begin #60; repeat (25) begin a <= ~a; #200; end end //toggle b and setup vcd dump initial begin $dumpfile("dmp_top.vcd"); //read verilog book for more info on system command $dumpvars(0,top); #60; $dumpon; repeat (10) begin b <= ~b; #500; end $dumpoff; $finish; //ends simulation end //Module under test top uut(.clk(clk), .a(a), .b(b), .c_in(c_in), .sum(sum), .c_out(c_out)); endmodule 8. Now comes the time to create a synthesized top level design from {full_adder.v top.v}. We are interested in creating a synthesized version of “top”. At command prompt type the following: Synopsys design_vision Now a design_vision gui has started up. In this gui follow these steps: In Menu: File --> Analyze. A Dialog box will appear called “Analyze Designs”. Click the “Add..” button and add every design file {full_adder.v top.v}. You can do this one file at a time or all at one time by using the CTRL key to select multiple files. After adding all the files press OK. In Menu: Design --> Elaborate. A Dialog box will appear called “Elaborate Designs”. There will be a drop down selection menu called “Design”. In this selection menu there will be two objects listed: top(verilog) and full_adder(verilog). Make sure that top(verilog) is selected. Press OK. Now in the Design Vision the “Hier 1” window will have objects listed in it. In Menu: Design --> Compile. In the dialog box that shows up press OK. In Menu: File --> Save As. Save the design as a verilog design with a new name (ex. top_syn.v). 9. Exit the gui and in the command prompt type exit to quit out of the design_vision_xg_t shell. Then type exit again to quit Synopsys. 10. Now it is time to simulate the synthesized design, top_syn.v, with the testbench, tb_top.v. The verilog simulator program of Synopsys is called VCX. The first step is to write a script for the simulation: #vcs_script.scr #This is a script file for VCX simulator ./tb_top.v ./top_syn.v -v ./iit018_stdcells.v +libext+.v +nolibcell +define+VPD+SAIF+VCD+SDF 11. At command prompt type: Synopsys Now type: vcs -f vcs_script.scr The result of running this command is that an executable called simv is created. 12. Run simv : ./simv 13. Now the file dmp_top.vcd has been created. 14. Now we will use a tool called PrimeTime-Px to get power estimation. The following script called power.scr will be used. #power.scr set power_enable_analysis TRUE set target_library "/home/syedh/iit_stdcells/lib/tsmc018/lib/iit018_stdcells.db" set link_library "/home/syedh/iit_stdcells/lib/tsmc018/lib/iit018_stdcells.db *" read_db $target_library read_verilog top_syn.v current_design test_inverter link read_vcd dmp_top.vcd -strip_path tb_top/uut create_power_waveforms –output vcd report_power 15. At the Synopsys command prompt type: pt_shell Now run the power.scr: source power.scr 16. If all went right the output from the script should look something like this: ====================================================================== Summary: Total number of nets = 11 Number of annotated nets = 11 (100.00%) Total number of leaf cells = 7 Number of fully annotated leaf cells = 7 (100.00%) ====================================================================== Information: The waveform options are: File name: power_waves.fsdb File format: fsdb Time interval: 0.01ns Hierarchical level: all Information: Power analysis is running, please wait ... Information: analysis is done for time window (0ns - 5050ns) **************************************** Report : Event Based Power Design : top Version: Z-2007.06-SP3 Date : Wed Feb 13 14:34:11 2008 **************************************** Attributes ---------- i - Including register clock pin internal power u - User defined power group Internal Switching Leakage Total Power Group Power Power Power Power ( %) Attrs -------------------------------------------------------------------------------- io_pad 0.0000 0.0000 0.0000 0.0000 ( 0.00%) memory 0.0000 0.0000 0.0000 0.0000 ( 0.00%) black_box 0.0000 0.0000 0.0000 0.0000 ( 0.00%) clock_network 3.292e-06 0.0000 0.0000 3.292e-06 (58.67%) i register 6.722e-07 4.735e-07 4.822e-10 1.146e-06 (20.42%) combinational 8.640e-07 3.086e-07 4.037e-10 1.173e-06 (20.90%) sequential 0.0000 0.0000 0.0000 0.0000 ( 0.00%) Net Switching Power = 7.821e-07 (13.94%) Cell Internal Power = 4.828e-06 (86.05%) Cell Leakage Power = 8.859e-10 ( 0.02%) --------- Total Power = 5.611e-06 (100.00%) X Transition Power = 0.0000 Glitching Power = 2.152e-08 Peak Power = 4.726e-03 Peak Time = 550.100