bus总线上的max_capacitance违例该如何修？

whynoreason · 发表于 2013-5-27 15:31:22

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本帖最后由 whynoreason 于 2013-5-27 15:32 编辑

总线bus三态的单元，相信大家都知道。通过工艺库lib里头的max_capacitance的计算，可以得出大概总线上可以挂的三态单元个数为45个。
可是设计中是有64个寄存器的，明显上挂不了64个。修改工艺库的话，工程量太大。
DC综合时，综合能通过，report_constaints -all时会有max_capaticance违例。从设置set_max_capacitance后再compile_ultra，都一样没办法搞定。
从DC到ICC，再到PT，全部提示max_capacitance违例的问题，请各位大虾支招。

目前自己觉得总线上寄存器的写入和读出，分属与两个不同的周期，应该不会互相干扰到。max_capacitance虽然达不到，波形会恶化，但应该还是能实现功能？

还有在做hold time check时，如何设置set_output_delay -min的值呢？用0的话似乎很难搞定。这个值一般有何经验值呢？

望各位大虾支招了。万分感谢！PT后的违例数据：

                           Required       Actual
Pin                   Capacitance Capacitance    Slack
-----------------------------------------------------------------
I6900/U3/N01             1.8318       2.5024       -0.6706  (VIOLATED)
I179/I5347/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I179/TRINV247/Y_tri/N01 1.8350       2.5024       -0.6674  (VIOLATED)
I179/TRINV255/Y_tri/N01 1.8350       2.5024       -0.6674  (VIOLATED)
I180/I7186/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I180/I7218/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I180/I7367/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I217/I5870/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I217/I6711/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I217/TRINV244/Y_tri/N01 1.8350       2.5024       -0.6674  (VIOLATED)
I218/I7262/Y_tri/N01    1.8350       2.5024       -0.6674  (VIOLATED)
I5374/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5826/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5871/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5908/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5917/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5930/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5936/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I5948/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6027/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6036/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6039/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6138/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6193/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6306/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6388/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6422/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6625/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6757/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I6903/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
I7269/Y_tri/N01          1.8350       2.5024       -0.6674  (VIOLATED)
TRINV268/Y_tri/N01       1.8350       2.5024       -0.6674  (VIOLATED)
TRINV271/Y_tri/N01       1.8350       2.5024       -0.6674  (VIOLATED)
TRINV274/Y_tri/N01       1.8350       2.5024       -0.6674  (VIOLATED)
TRINV278/Y_tri/N01       1.8350       2.5024       -0.6674  (VIOLATED)
TRINV285/Y_tri/N01       1.8350       2.5024       -0.6674  (VIOLATED)
TRINV287/Y_tri/N01       1.8350       2.5024       -0.6674  (VIOLATED)