后仿验证的ABC

后仿检查

数模接口
异步路径
时序紧张的同步路径
时钟和复位
不定态扩散问题

重要用例和场景

启动
复位
时钟切换

后仿网表

post-synth netlist
post-dft netlist
post-pnr netlist
post-pnr netlist with PG

通常后仿用例

跨时钟域异步关系
上下电和启动流程
数模接口时序关系
时钟复位相关：时钟无毛刺切换、复位去毛刺滤波、复位解复位顺序等
加了false path或multicycle path的路径
对时钟加频偏
memory内容初始化或不初始化

检查

复位后，register X态
复位后，重要模块输入输出状态

Violation处理

violation file
- 跨时钟域数据传输同步的第一级DFF
- 异步复位同步释放电路的Rn和CK端之间Path
POR复位生效前的violation log需要忽略
violation log要按IP模块划分
提供各个violation log的waive方法，建议用脚本处理后给设计者review

X态分析

遇到X态，试着从以下几个角度分析。

是否所有的DUT input端口都给予了一个确定值?
没有复位端的寄存器有没有作初始化?
DUT里有哪些Memory, 是否有必要进行初始化？
如果是Timing violation引起的X态，则需要先分析Timing violation

对环境建议

环境中不要用force
不要过多使用编译期宏
把变化控制留在runtime

VCS相关

options

use for zero delay GLS

+nospecify
+notimingcheck

don't use them for Post-PR netlist

VCS options

-sdf min|typ|max:instance_name:file.sdf
+sdfverbose
+optconfigfile=noTiming.cfg
-sdf_logfile

noTiming Config file Format

module {list_of_module_identifiers} {list_of_attributes};

instance {list_of_module_identifiers_and_hierarchical_names} {list_of_attributes};

tree [(depth)] {list_of_module_identifiers} {list_of_attributes};

Attributes for timing:

noIopath: Disables module path delays in the specified module instances.
Iopath: Enables module path delays in the specified module instances.
noSpecify: Disables the specify blocks in the specified module instances.
Specify: Enables specify blocks in the specified module instances.
noTiming: Disables timing checks in the specified module instances.
Timing: Enables timing checks in the specified module instances.

举例：
后端提供一个sync cell的list, 然后写成noTiming config file.

instance {tb_top.u_dut.u_sync_cell0} {noTiming};

system task for sdf

$sdf_annotate ("sdf_file"[, module_instance] [,"sdf_configfile"][,"sdf_logfile"][,"mtm_spec"] [,"scale_factors"][,"scale_type"]);

"sdf_file": Specifies the path to an SDF file.
module_instance: Specifies the scope where back-annotation starts. The default is the scope of the module instance that calls $sdf_annotate.
"sdf_configfile": Specifies the SDF configuration file. For more information on the SDF configuration file, see the “SDF Configuration File” section.
"sdf_logfile": Specifies an SDF log file to which VCS sends error messages and warnings. By default, VCS displays no more than ten warnings and ten error messages about back-annotation and writes no more than that in the log file you specify with the -l option. However, if you specify the SDF log file with this argument, the SDF log file receives all messages about back-annotation. You can also use the +sdfverbose runtime option to enable the display of all back-annotation messages.
"mtm_spec": Specifies which delay values of min:typ:max triplets VCS back- annotates. Its possible values are "MINIMUM", "TYPICAL", "MAXIMUM", or "TOOL_CONTROL" (default).
"scale_factors": Specifies the multiplier for the minimum, typical, and maximum components of delay triplets. It is a colon separated string of three positive, real numbers "1.0:1.0:1.0" by default.
"scale_type": Specifies the delay value from each triplet in the SDF file for use before scaling. Its possible values are "FROM_TYPICAL", "FROM_MIMINUM", "FROM_MAXIMUM", and "FROM_MTM" (default).