SiliconSmart - Part0

本文介绍Synopsys的特征化和建模工具SiliconSmart。

SiliconSmart 介绍

SiliconSmart 是业界领先的特征化(Characterization)和建模(Modeling)工具。其支持的建模类型包括.

Nonlinear Delay Model (NLDM) for timing analysis
Nonlinear Power Model (NLPM) for power analysis
Composite Current Source Models (CCS) for timing and power
Cadence Effective Current Source Models (ECSM) for timing and power
I/O Buffer Information Specifications (IBIS)

可以理解为，SiliconSmart 是一种建立单元库的工具，通过它得到我们在综合及后端实现过程中使用的 .db 文件，用于后续工作。

数据流程

SiliconSmart的工作流程如下，详细过程请参阅SiliconSmart UserGuide.

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其工作流程主要分为4种模式

Recharacterization Flow — This approach will recharacterize data in an existing Liberty model or add new data to an existing Liberty model.
Function-Based Flow — The function-based approach uses functions to automatically determine configuration.
Structure-Based Flow — A function-based approach that uses functions and automatic vector simulation based on the structure of the circuit.
Sequence-Based Flow — The sequence based approach adds a user-defined input stimulus to specify arcs to be characterized and the sequence to be performed, without using automated methods.

由于我们的工作并非自己建立标准单元库，而是在已有单元库的基础上，尝试通过降低工作电压来降低功耗，因此使用上方的 Recharacterization Flow。之后的内容也基于该 Flow 展开。

工作准备

Vendor 提供的 Liberty .lib 文件。作为我们re-char flow的参考。
Vendor 提供的标准单元post-layout netlist 网表文件。与前端网表的区别在于，增加了寄生RC。如果 Vendor 提供的 netlist 将所有单元包括在同一文件中，需自己将其分开到单独的netlist，每个文件名与标准单元名称对应。统一放在 ./netlist 文件夹下。
Vendor 提供的 PDK 下的 model 文件。注意，model文件类型与选择的仿真器需一致。例如我们使用 hspice 作为仿真器，则使用${PDK_MODEL_DIR}/hspice/下的model文件。该文件夹下有多个文件，PDK安装时已经自动配置好，我们使用顶层的 toplevel.l 即可。

脚本编写

此处仅展示SiliconSmart Re-Char Flow过程用到的脚本。具体的讲解放在之后的博文中。

configure.tcl - SiliconSmart设置文件

create_operating_condition op_cond_new

# set Power Supply Voltage and temperature here
add_opc_supplies op_cond_new COREVDD1 0.8
add_opc_grounds op_cond_new COREGND1 0
set_opc_temperature op_cond_new 25

# set Process here
set_opc_process on_cond_all [subst { { .lib '${PDK_MODEL_DIR}/hspice/toplevel.l' TOP_TT}}]

set_config_opt voltage_name_map {COREVDD1 VDD COREGND1 VSS}

define_parameter default {

    # one active pvt for one confugire.tcl file
    set active_pvts {op_cond_new} 

    # HSPICE
    set simulator hspice 
    set simulator_cmd {hspice <input_deck> -o <listing_file> }

    # HSPICE Options
    set simulator_options {
        "common,hspice: probe=1 runlvl=5 numdgt=7 measdgt=7 acct=1 nopage"
    }

    # Simulation Resolution
    set time_res_high 1e-12
    set time_res_low 1e-10

    # Controls which supplies are measured for power consumption
    set power_meas_supplies {VDD}

    # list of grounds supplies used (required for Functional Recognition)
    set power_meas_grounds {VSS}

    # specifies which multi-rail format to be used in Liberty model: none, v1, or v2
    set liberty_multi_rail_format v2

    set slew_derate_upper_threshold 0.9
    set slew_derate_lower_threshold 0.1

    set liberty_max_transition 2
    set liberty_max_capacitance 0.1
    # set liberty_max_capacitance_mode 1

    set archive_condition_on_success compress
    set archive_condition_on_failure yes

    set constraint_mode independent 
    set smc_constraint_style relative_degradation
    set smc_degrade 0.1
    set path_constraint_mode off

    set model_normalized_driver_waveform 0
    set insert_liberty_default_ndw 0
    set merge_pin_ndw_groups 0

    # LOAD SHARE PARAMETERS
    #  job_scheduler: 'lsf' (Platform), 'grid' (SunGrid), or 'standalone` (local machine)
    set job_scheduler standalone
    set run_list_maxsize 24
    set normal_queue (bnormal -R rusage[mem=4000])
}
############################
# DEFAULT PINTYPE PARAMETERS
############################

pintype default {
    set total_slew_multiplier 1.0

    set logic_high_name VDD
    set logic_high_threshold 0.7

    set logic_low_name VSS
    set logic_low_threshold 0.3

    set prob_delay_level 0.5

    # Number of slew and load indices 
    # (when importing with -use_default_slews -use_default_loads)

    set numsteps_slew 5
    set numsteps_load 5
    set constraint_numsteps_slew 3

    # Operating load ranges
    set smallest_load 10e-15
    set largest_load 90e-15
    set autorange_load state

    # operating slew ranges
    set smallest_slew 10.0e-12
    set largest_slew 5.0e-9
    set max_tout 5.0e-9

    # Automatically determine largest_load based on max_tout: off or on
    set autorange_load on

    # Noise of points in for noise height
    set numsteps_height 8

    # Input noise width
    set numsteps_width 5

    # driver model: pwl, emulated, active, active-waveform, custom
    set driver_mode emulated 

    # driver cell name (relevant only when driver_mode is `active`)
    # set driver pwl
}

#####################################
# LIBERTY_MODEL_GENERATION_PARAMETERS
#####################################
define_parameters liberty_model {
    # Add Liberty header attributes here for use with "model -create_new_model"
    set delay_model "table_lookup"
    set default_fanout_laod 1.0
    set default_inout_pin_cap 1.0
    set default_input_pin_cap 1.0
    set default_output_pin_cap 0.0
    set default_cell_leakage_power 0.0
    set in_place_swap_mode match_footpoint
}
#######################
# VALIDATION PARAMETERS 
#######################
define_parameter validation {
    # Add validation parameters here
}

cell.tcl - 设置需要re-char的cell列表

# replace with names of real cells in your library
set cells {CELL1 CELL2 CELL3}

run.tcl - SiliconSmart启动脚本

source ./cell.tcl
set charpoint testcase

set LIB_FILE ${DIGITAL_LIB_DIR}/${LIB}_ccs.lib 
set NETLIST_DIR ./netlist/

create $charpoint
set_log_file $charpoint/sis.log

exec cp configure.tcl ${charpoint}/config/configure.tcl
set_location $charpoint

set_config_opt simulator bisection 1
set_config_opt ccsn_rechar 1

import -fast -liberty ${LIB_FILE} -extention .cdl -netlist_dir ${NETLIST_DIR} $cells
configure -fast -timing -power -ccs -ccs_noise $cells


characterize $cells 

model -verilog -output my_models $cells
model -timing -power -ccs -ccs_noise -output ccs $cells

log_info "IAMDONE"

Makefile

all: clean run

run:
    bsub -Is siliconsmart run.tcl

clean:
    rm -rf ./testcase

2024 8
2021 12

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