set_path_margin这个命令一般什么情况下会使用

0417多音字

set_path_margin 1.2是约束更紧还是更轻松

fangwang85

应该是更紧了，用的比较少

randolpha

       set_path_margin
              Specifies  a  margin  to  adjust required times for paths in the
              current design.
DESCRIPTION
       This  command  adjusts  the data required time for specified paths by a
       specified amount, margin_value. The required time for any startpoint in
       from_list  to  any  endpoint  in to_list is adjusted by margin_value. A
       positive margin value results in a more restrictive or  tighter  check,
       whereas a negative margin value results in a less restrictive or looser
       check. Based on the type of timing constraint, either  setup  or  hold,
       the margin value is either subtracted from or added to the default data
       required time.

       The set_path_margin command is a point-to-point timing  exception  com-
       mand;  that  is, it adjusts the required time of the path and hence the
       endpoint slack for the timing paths.


EXAMPLES
       The  following  example shows how to adjust the required time to a port
       named Y by 10 units. The adjustment  results  in  a  more  restrictive,
       tighter timing constraint because the margin value is positive.

         prompt> set_path_margin 10.0 -to {Y}

       This  example  shows how to specify that the required time of all paths
       from cell ff1a or ff1b that pass through cell u1 and end at  cell  ff2e
       must be adjusted by 15.0 units.

         prompt> set_path_margin 15.0 -from {ff1a ff1b} -through {u1} -to {ff2e}

       This  example  shows how to specify that all paths to endpoints clocked
       by PHI2 must be adjusted by 8.5 units.

         prompt> set_path_margin 8.5 -to [get_clocks PHI2]

       This example specifies that all timing paths from  pin  ff1/CP  to  pin
       ff2/D  that  rise  through  at least one of pins U1/Z and U2/Z and fall
       through at least one of pins U3/Z and U4/C  must  be  adjusted  by  8.0
       units.

         prompt> set_path_margin 8.0 -from {ff1/CP} -to {ff2/D} \
            -rise_through {U1/Z U2/Z} -fall_through {U3/Z U4/C}

randolpha

       set_path_margin
              Specifies  a  margin  to  adjust required times for paths in the
              current design.

DESCRIPTION
       This  command  adjusts  the data required time for specified paths by a
       specified amount, margin_value. The required time for any startpoint in
       from_list  to  any  endpoint  in to_list is adjusted by margin_value. A
       positive margin value results in a more restrictive or  tighter  check,
       whereas a negative margin value results in a less restrictive or looser
       check. Based on the type of timing constraint, either  setup  or  hold,
       the margin value is either subtracted from or added to the default data
       required time.

       The set_path_margin command is a point-to-point timing  exception  com-
       mand;  that  is, it adjusts the required time of the path and hence the
       endpoint slack for the timing paths.

EXAMPLES
       The  following  example shows how to adjust the required time to a port
       named Y by 10 units. The adjustment  results  in  a  more  restrictive,
       tighter timing constraint because the margin value is positive.

         prompt> set_path_margin 10.0 -to {Y}

       This  example  shows how to specify that the required time of all paths
       from cell ff1a or ff1b that pass through cell u1 and end at  cell  ff2e
       must be adjusted by 15.0 units.

         prompt> set_path_margin 15.0 -from {ff1a ff1b} -through {u1} -to {ff2e}

       This  example  shows how to specify that all paths to endpoints clocked
       by PHI2 must be adjusted by 8.5 units.

         prompt> set_path_margin 8.5 -to [get_clocks PHI2]

       This example specifies that all timing paths from  pin  ff1/CP  to  pin
       ff2/D  that  rise  through  at least one of pins U1/Z and U2/Z and fall
       through at least one of pins U3/Z and U4/C  must  be  adjusted  by  8.0
       units.

         prompt> set_path_margin 8.0 -from {ff1/CP} -to {ff2/D} \
            -rise_through {U1/Z U2/Z} -fall_through {U3/Z U4/C}