数字后端问题求助

雷郑雨100613

本人在使用Encounter做后端设计，碰到以下警告，不知道该如何处理？这些引脚都是模块的端口信号，端口驱动单元设置成一个与非门（尺寸有换过，但是警告还是有，而且数值都一样。

同时本人一直有一个疑问，对端口设置约束，有两种方法，一个是使用set_input_transition -min -max，另外一个是使用set_driving_cell。使用第一个方法，我们可以设置成极端情况对端口的输入转换时间的分别设置最大值和最小值，软件可以根据这个值计算后级的门的延时（根据输入转换时间和输出负载进行查找）。
而当我们使用set_driving_cell时，好处在与这个单元的延时信息会随着PVT变化，但是这里一直有个疑问。当设置driving_cell时，我们并没有设置这个driving_cell的输入转换时间，软件是默认其输入转换时间为0进行计算吗？如果这样，该门的计算出来的转换时间很小，会小于查找表中最小的值，这个是否可能是以下警告的原因？

**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:RXDATA, Cell type : TOP, Arc : Iv->ZN^ because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:RXDATA, Cell type : TOP, Arc : I^->ZNv because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:SELECT, Cell type : TOP, Arc : Iv->ZN^ because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:SELECT, Cell type : TOP, Arc : I^->ZNv because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:vramp_ct_sel_inv, Cell type : TOP, Arc : Iv->ZN^ because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:vramp_ct_sel_inv, Cell type : TOP, Arc : I^->ZNv because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:bg_adj_inv[1], Cell type : TOP, Arc : Iv->ZN^ because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:bg_adj_inv[1], Cell type : TOP, Arc : I^->ZNv because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:bg_adj_inv[0], Cell type : TOP, Arc : Iv->ZN^ because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.
**WARN: (ENCESI-3025):
Delay calculation was forced to extrapolate the slew on instance mipi_rffe_if_wrapper:bg_adj_inv[0], Cell type : TOP, Arc : I^->ZNv because it's outside the characterized table range. The actual slew is 0.0118 ns and the lower bound in the table is 0.0375 ns. In some cases, extrapolation can reduce the accuracy of delay calculation.

hwesnd

ICC可以指定from pin的transition的，Encounter没有吗

icc_shell> set_driving_cell -help
Usage: set_driving_cell    # set driving cell
        [-cell obsolete - please use -lib_cell instead]
                               (obsolete option)
        [-lib_cell library_cell_name]
                               (library cell)
        [-rise]                (set rise driving_cell info)
        [-fall]                (set fall driving_cell info)
        [-min]                 (set min driving_cell info)
        [-max]                 (set max driving_cell info)
        [-library lib_name]    (library of driving cell)
        [-pin pin_name]        (driving pin name)
        [-from_pin from_pin_name]
                               (specifies the from-pin)
        [-multiply_by factor]  (transition multiplier:
                                Value >= 0)
        [-input_transition_rise transition]
                               (input transition rise time for the from_pin:
                                Value >= 0)
        [-input_transition_fall transition]
                               (input transition fall time for the from_pin:
                                Value >= 0)
        [-dont_scale]          (prevent operating condition scaling)
        [-none]                (remove previous driving_cell info)
        [-no_design_rule]      (do not infer design rules from driving cell)
        port_list              (list of input ports)