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ASIC Front-End Design

ECE 448 Lecture 20. ASIC Front-End Design. Two competing implementation approaches. FPGA F ield P rogrammable G ate A rray. ASIC A pplication S pecific I ntegrated C ircuit. designed all the way from behavioral description to physical layout. no physical layout design;

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ASIC Front-End Design

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  1. ECE 448 Lecture 20 ASIC Front-End Design ECE 448 – FPGA and ASIC Design with VHDL

  2. Two competing implementation approaches FPGA FieldProgrammable GateArray ASIC ApplicationSpecific IntegratedCircuit • designed all the way • from behavioral description • to physical layout • no physical layout design; • design ends with • a bitstream used • to configure a device • designs must be sent • for expensive and time • consuming fabrication • in semiconductor foundry • bought off the shelf • and reconfigured by • designers themselves ECE 448 – FPGA and ASIC Design with VHDL

  3. FPGAs vs. ASICs FPGAs ASICs Off-the-shelf High performance Low development costs Low power Short time to the market Low cost (but only in high volumes) Reconfigurability ECE 448 – FPGA and ASIC Design with VHDL

  4. ASIC Design Example – Factoring circuit/GMU Global Memory Local Memory ECE 448 – FPGA and ASIC Design with VHDL

  5. ASIC 130 nm vs. Virtex II 6000 Factoring/GMU 19.80 mm 51x Area of Xilinx Virtex II 6000 FPGA (estimation by R.J. Lim Fong, MS Thesis, VPI, 2004) 19.68 mm 2.7 mm 2.82 mm Area of an ASIC with equivalent functionality ECE 448 – FPGA and ASIC Design with VHDL

  6. ASICs vs. FPGAs Source: I. Kuon, J. Rose, University of Toronto “Measuring the Gap Between FPGAs and ASICs” IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, vol. 62, no. 2, Feb 2007. ECE 448 – FPGA and ASIC Design with VHDL

  7. ASICs vs. FPGAs 23 representative circuits implemented using FPGAs and ASICs - computer arithmetic (booth, cordic18, cordic8, etc.) - digital signal processing (rs_encoder, fir3, fir24, etc.) - communications (ethernet, mac1, atm, etc.) - cryptography (des_area, des_perf, aes, aes192, etc.) - scientific computations (molecular, raytracer, etc.) ECE 448 – FPGA and ASIC Design with VHDL

  8. ECE 448 – FPGA and ASIC Design with VHDL

  9. ECE 448 – FPGA and ASIC Design with VHDL

  10. ECE 448 – FPGA and ASIC Design with VHDL

  11. ECE 448 – FPGA and ASIC Design with VHDL

  12. Simplified ASIC Design Flow Synthesis Front-End Design Timing Analysis Floorplanning Back-End Design Placement Clock Tree Synthesis Routing Design for Manufacturing 31 ECE 448 – FPGA and ASIC Design with VHDL

  13. Major ASIC Toolsets Cadence Magma ECE 448 – FPGA and ASIC Design with VHDL

  14. Simplified ASIC Design Flow Synopsys Tools Synthesis Design Compiler Front-End Design Primetime Timing Analysis Floorplanning Back-End Design Placement Astro Clock Tree Synthesis Routing Design for Manufacturing 31 ECE 448 – FPGA and ASIC Design with VHDL

  15. A Complete Placed and Routed Chip IP 28 ECE 448 – FPGA and ASIC Design with VHDL

  16. What is “Physical Layout”? VDD VDD PMOS PMOS OUT IN IN OUT NMOS NMOS GND GND Transistor or Device View Physical or Layout View Physical Layout – Topography of devices and interconnects, made up of polygons that represent different layers of material (diffusion, polysilicon, metal, contact, etc) ECE 448 – FPGA and ASIC Design with VHDL

  17. Process of Device Fabrication Silicon Substrate Layout or Mask (aerial) view • Devices are fabricated vertically on a silicon substrate wafer by layering different materials in specific locations and shapes on top of each other • Each of many process masks defines the shapes and locations of a specific layer of material (diffusion, polysilicon, metal, contact, etc) • Mask shapes, derived from the layout view, are transformed to silicon via photolithographic and chemical processes Wafer (cross-sectional) view 40 ECE 448 – FPGA and ASIC Design with VHDL

  18. Wafer Representation of Layout Polygons 0.25 um Input PMOS VDD Output GND NMOS Aerial or Layout View Wafer Cross-sectional View 41 ECE 448 – FPGA and ASIC Design with VHDL

  19. Front-End Design Flow ECE 448 – FPGA and ASIC Design with VHDL

  20. Simplified RTL Synthesis Write RTL HDL Code HDL No Simulate OK Yes Synthesize RTL Code to Gates Gate Level Netlist No Constraints Met? Yes No Gate Level Testing OK? Yes Proceed with Backend Processing ECE 448 – FPGA and ASIC Design with VHDL

  21. VHDL vs. Verilog ECE 448 – FPGA and ASIC Design with VHDL

  22. Logic Synthesis VHDL description Circuit netlist architecture MLU_DATAFLOW of MLU is signal A1:STD_LOGIC; signal B1:STD_LOGIC; signal Y1:STD_LOGIC; signal MUX_0, MUX_1, MUX_2, MUX_3: STD_LOGIC; begin A1<=A when (NEG_A='0') else not A; B1<=B when (NEG_B='0') else not B; Y<=Y1 when (NEG_Y='0') else not Y1; MUX_0<=A1 and B1; MUX_1<=A1 or B1; MUX_2<=A1 xor B1; MUX_3<=A1 xnor B1; with (L1 & L0) select Y1<=MUX_0 when "00", MUX_1 when "01", MUX_2 when "10", MUX_3 when others; end MLU_DATAFLOW; ECE 448 – FPGA and ASIC Design with VHDL

  23. Basic Synthesis Flow ECE 448 – FPGA and ASIC Design with VHDL

  24. Synthesis using Design Compiler ECE 448 – FPGA and ASIC Design with VHDL

  25. ECE 448 – FPGA and ASIC Design with VHDL

  26. ECE 448 – FPGA and ASIC Design with VHDL

  27. Script Language:TCL – Tool Command Language • Created by John Ousterhout of UC Berkeley • Scripting Language • Very simple to automate routine tasks. • Extension Language • Used to customize tools with user/company specific aplications. • Nearly all of modern EDA tools have a TCL interface. • Very simple to learn and use. ECE 448 – FPGA and ASIC Design with VHDL

  28. TCL References • Practical Programming in Tcl and TK • Brent B. Welch • Ken Jones • TCL/TK in a Nutshell • Paul Raines • Jeff Tranter ECE 448 – FPGA and ASIC Design with VHDL

  29. Synthesis script (1) designer = "Pawel Chodowiec" company = "George Mason University" search_path = "./opt3/synopsys/TSMCHOME/digital/Front_End/timing_power/tcb013ghp_200a " link_library = "* tcb013ghptc.db" /* Typical case library */ target_library = "tcb013ghptc.db " symbol_library = "tcb013ghp.sdb " /* Directory configuration */ src_directory = ~/exam1/vhdl/ report_directory = ~/exam1/reports/ db_directory = ~/exam1/db/ ECE 448 – FPGA and ASIC Design with VHDL

  30. Synthesis script (2) /* Packages can be only read */ read_file -format vhdl -rtl src_directory + "components.vhd" blocks = {regne, upcount, RAM_16Xn_DISTRIBUTED, exam1} foreach (block, blocks) { block_source = src_directory + block + ".vhd" read_file -format vhdl -rtl block_source analyze -format vhdl -lib WORK block_source } current_design block /* All commands now apply to the entity "exam1" */ ECE 448 – FPGA and ASIC Design with VHDL

  31. Synthesis script (3) uniquify /* Creates unique instances of multiple refrenced entities */ link check_design /* Checks the current design for consistency */ /*******************************************/ /* apply block attributes and constraints */ /*******************************************/ create_clock -period 10 clk /* Defines that the port "clk" on the entity "clk" is the clock for the design. Period=10ns 50% duty cycle Use -waveform option to define duty cycle other than 50%*/ set_operating_conditions NCCOM /*Normal Case Commercial Operating Conditions*/ ECE 448 – FPGA and ASIC Design with VHDL

  32. Synthesis script (4) /***************************************************/ /* Apply these constraints to the top-level entity*/ /***************************************************/ set_max_fanout 100 block set_clock_latency 0.1 find(clock, "clk") set_clock_transition 0.01 find(clock, "clk") set_clock_uncertainty -setup 0.1 find(clock, "clk") set_clock_uncertainty -hold 0.1 find(clock, "clk") set_load 0 all_outputs() set_input_delay 1.0 -clock clk -max all_inputs() set_output_delay -max 1.0 -clock clk all_outputs() set_wire_load_model -library tcb013ghptc -name "TSMC8K_Fsg_Conservative" ECE 448 – FPGA and ASIC Design with VHDL

  33. Wireloadmodelbasics (1) ECE 448 – FPGA and ASIC Design with VHDL

  34. Wireloadmodelbasics (2) ECE 448 – FPGA and ASIC Design with VHDL

  35. Synthesis script (5) set_dont_touch block compile -map_effort medium change_names -rules vhdl vhdlout_architecture_name = "sort_syn" vhdlout_use_packages = {"IEEE.std_logic_1164"} write -f db -hierarchy -output db_directory + "exam1.db" /*write -f vhdl -hierarchy -output db_directory + "exam1_syn.vhd"*/ report -area > report_directory + "exam1.report_area" report -timing -all > report_directory + "exam1.report_timing" ECE 448 – FPGA and ASIC Design with VHDL

  36. Results of synthesis ECE 448 – FPGA and ASIC Design with VHDL

  37. Area report after synthesis (1) report_area Information: Updating design information... (UID-85) **************************************** Report : area Design : exam1 Version: V-2003.12-SP1 Date: Tue Nov 15 20:39:06 2005 **************************************** Library(s) Used: tcb013ghptc (File: /opt3/synopsys/TSMCHOME/digital/Front_End/timing_power/ tcb013ghp_200a/tcb013ghptc.db) ECE 448 – FPGA and ASIC Design with VHDL

  38. Area report after synthesis (2) Number of ports: 75 Number of nets: 346 Number of cells: 107 Number of references: 28 Combinational area: 10593.477539 Noncombinational area: 14295.521484 Net Interconnect area: undefined (Wire load has zero net area) Total cell area: 24888.976562 Total area: undefined ECE 448 – FPGA and ASIC Design with VHDL

  39. Critical Path (1) out in clk D D Q Q • Critical Path – The Longest Path From Outputs of Registers to Inputs of Registers t logic tCritical = tFF-P + tlogic + tFF-setup ECE 448 – FPGA and ASIC Design with VHDL

  40. Critical Path (2) • Min. Clock Period = Length of The Critical Path • Max. Clock Frequency = 1 / Min. Clock Period ECE 448 – FPGA and ASIC Design with VHDL

  41. n+m n+m ECE 448 – FPGA and ASIC Design with VHDL

  42. Clock Jitter • Rising Edge of The Clock Does Not Occur Precisely Periodically • May cause faults in the circuit clk ECE 448 – FPGA and ASIC Design with VHDL

  43. Clock Skew out in clk delay out in D D Q Q D D Q Q clk delay • Rising Edge of the Clock Does Not Arrive at Clock Inputs of All Flip-flops at The Same Time ECE 448 – FPGA and ASIC Design with VHDL

  44. Timing report after synthesis (1) **************************************** Report : timing -path full -delay max -max_paths 1 Design : exam1 Version: V-2003.12-SP1 Date : Tue Nov 15 20:39:06 2005 **************************************** Operating Conditions: NCCOM Library: tcb013ghptc Wire Load Model Mode: segmented ECE 448 – FPGA and ASIC Design with VHDL

  45. Timing report after synthesis (2) Startpoint: in_addr(1) (input port clocked by clk) Endpoint: RegSUM/Q_reg[34] (rising edge-triggered flip-flop clocked by clk) Path Group: clk Path Type: max Des/Clust/Port Wire Load Model Library ----------------------------------------------------------------------------------- exam1 TSMC8K_Fsg_Conservative tcb013ghptc RAM_16Xn_DISTRIBUTED ZeroWireload tcb013ghptc exam1_DW01_cmp2_32_0 ZeroWireload tcb013ghptc exam1_DW01_cmp2_32_1 ZeroWireload tcb013ghptc exam1_DW01_add_35_0 ZeroWireload tcb013ghptc regne_1 ZeroWireload tcb013ghptc regne_2 ZeroWireload tcb013ghptc regne_n35 ZeroWireload tcb013ghptc ECE 448 – FPGA and ASIC Design with VHDL

  46. Timing report after synthesis (3) Point Incr Path ------------------------------------------------------------------------------------------------ clock clk (rise edge) 0.00 0.00 clock network delay (ideal) 0.10 0.10 input external delay 1.00 1.10 f in_addr(1) (in) 0.00 1.10 f U98/Z (CKMUX2D1) 0.13 1.23 f Memory/ADDR[1] (RAM_16Xn_DISTRIBUTED) 0.00 1.23 f Memory/U41/ZN (INVD1) 0.08 1.31 r Memory/U343/Z (OR3D1) 0.10 1.41 r Memory/U338/ZN (INVD2) 0.20 1.61 f Memory/U40/ZN (MOAI22D0) 0.17 1.78 f Memory/U350/Z (OR4D1) 0.26 2.03 f Memory/DATA_OUT[0] (RAM_16Xn_DISTRIBUTED) 0.00 2.03 f ECE 448 – FPGA and ASIC Design with VHDL

  47. Timing report after synthesis (4) add_96xplusxplus/B[0] (exam1_DW01_add_35_0) 0.00 2.03 f add_96xplusxplus/U9/Z (AN2D0) 0.12 2.15 f add_96xplusxplus/U1_1/CO (CMPE32D1) 0.10 2.25 f add_96xplusxplus/U1_2/CO (CMPE32D1) 0.10 2.34 f add_96xplusxplus/U1_3/CO (CMPE32D1) 0.10 2.44 f add_96xplusxplus/U1_4/CO (CMPE32D1) 0.10 2.54 f add_96xplusxplus/U1_5/CO (CMPE32D1) 0.10 2.63 f add_96xplusxplus/U1_6/CO (CMPE32D1) 0.10 2.73 f add_96xplusxplus/U1_7/CO (CMPE32D1) 0.10 2.82 f add_96xplusxplus/U1_8/CO (CMPE32D1) 0.10 2.92 f add_96xplusxplus/U1_9/CO (CMPE32D1) 0.10 3.02 f add_96xplusxplus/U1_10/CO (CMPE32D1) 0.10 3.11 f add_96xplusxplus/U1_11/CO (CMPE32D1) 0.10 3.21 f add_96xplusxplus/U1_12/CO (CMPE32D1) 0.10 3.31 f add_96xplusxplus/U1_13/CO (CMPE32D1) 0.10 3.40 f add_96xplusxplus/U1_14/CO (CMPE32D1) 0.10 3.50 f ECE 448 – FPGA and ASIC Design with VHDL

  48. Timing report after synthesis (5) add_96xplusxplus/U1_15/CO (CMPE32D1) 0.10 3.60 f add_96xplusxplus/U1_16/CO (CMPE32D1) 0.10 3.69 f add_96xplusxplus/U1_17/CO (CMPE32D1) 0.10 3.79 f add_96xplusxplus/U1_18/CO (CMPE32D1) 0.10 3.88 f add_96xplusxplus/U1_19/CO (CMPE32D1) 0.10 3.98 f add_96xplusxplus/U1_20/CO (CMPE32D1) 0.10 4.08 f add_96xplusxplus/U1_21/CO (CMPE32D1) 0.10 4.17 f add_96xplusxplus/U1_22/CO (CMPE32D1) 0.10 4.27 f add_96xplusxplus/U1_23/CO (CMPE32D1) 0.10 4.37 f add_96xplusxplus/U1_24/CO (CMPE32D1) 0.10 4.46 f add_96xplusxplus/U1_25/CO (CMPE32D1) 0.10 4.56 f add_96xplusxplus/U1_26/CO (CMPE32D1) 0.10 4.66 f add_96xplusxplus/U1_27/CO (CMPE32D1) 0.10 4.75 f add_96xplusxplus/U1_28/CO (CMPE32D1) 0.10 4.85 f add_96xplusxplus/U1_29/CO (CMPE32D1) 0.10 4.94 f add_96xplusxplus/U1_30/CO (CMPE32D1) 0.10 5.04 f add_96xplusxplus/U1_31/CO (CMPE32D1) 0.10 5.14 f ECE 448 – FPGA and ASIC Design with VHDL

  49. Timing report after synthesis (6) add_96xplusxplus/U7/Z (AN2D0) 0.10 5.24 f add_96xplusxplus/U5/Z (AN2D0) 0.08 5.32 f add_96xplusxplus/U4/Z (CKXOR2D0) 0.15 5.47 f add_96xplusxplus/SUM[34] (exam1_DW01_add_35_0) 0.00 5.47 f RegSUM/R[34] (regne_n35) 0.00 5.47 f RegSUM/U32/Z (AO21D0) 0.11 5.57 f RegSUM/Q_reg[34]/D (EDFQD1) 0.00 5.57 f data arrival time 5.57 ECE 448 – FPGA and ASIC Design with VHDL

  50. Timing report after synthesis (7) clock clk (rise edge) 10.00 10.00 clock network delay (ideal) 0.10 10.10 clock uncertainty -0.10 10.00 RegSUM/Q_reg[34]/CP (EDFQD1) 0.00 10.00 r library setup time -0.12 9.88 data required time 9.88 ------------------------------------------------------------------------------------- data required time 9.88 data arrival time -5.57 ------------------------------------------------------------------------------------- slack (MET) 4.31 ECE 448 – FPGA and ASIC Design with VHDL

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