minNumCut

spacingTables(
( minNumCut tx_cutLayer 
 (( "width" nil nil ) 
  ['cutClass {f_cutWidth | (f_cutWidth f_cutLength) | t_name}
  ['diffCutClass]]
  ['distanceWithin f_within ['manhattan]]
  ['above | 'below | 'bothAboveBelow] 
  ['sameMetalOverlap | 'fullyEnclosed] 
  [f_default]
  ['otherWidth g_otherWidth] 
 )
 (g_table)
)

) ;spacingTables

Specifies the minimum number of cuts that a via object or a via instance must contain when connecting two wide wires or a wide wire and a pin. The number of via cuts required depends on the width of the wires. If 'distanceWithin is specified, only the via cuts that are within the specified distance from each other are counted.

Usually, wide wires carry more current, and if you change layers between two wide wires, you need a sufficient number of via cuts to carry an equivalent amount of current. Using multiple via cuts, instead of just one, also increases reliability.

The minNumCut constraint can be specified in the following constraint groups:

• Wire Edit: The minNumCut constraint can be specified in a wire edit constraint group, which can then be set as the default constraint group for creating and editing wires by using either the wireConstraintGroup environment variable or by selecting it in the Options – Editor – Default Wire Constraint Group list.
• Foundry: The definition of minNumCut in the wire edit constraint group overrides the minNumCut definition available in the foundry constraint group.
• Net: The minNumCut constraint can be specified for a particular net in a net constraint group. Currently, the router supports only a limited number of constraints in the net constraint group, including minWidth, minNumCut, minSpacing, validLayers, and validVias.

Values

tx_cutLayer	The cut layer on which the constraint is applied. Type: String (layer and purpose names) or Integer (layer number)
"width" nil nil
	This identifies the index for table.
g_table	The format of the table is as follows: (f_width x_numberOfCuts) where, f_width is the width of the wire. The width of the wire must be greater than or equal to this value for the number of corresponding via cuts to apply. x_numberOfCuts is the minimum number of cuts that a via must contain. Type: A 1-D table specifying floating-point width values and the number of via cuts required corresponding to different widths

Parameters

'cutClass {f_width | (f_width f_length) | t_name}
	The cut class to which the constraint applies, specified by width, by width and length, or by name (as defined in a cutClasses constraint). f_width: Width f_length: Length t_name: Name of the cut class
'diffCutClass	(Virtuoso Layout Suite EXL and higher tiers) This parameter specifies that if there is one cut belonging to the cut class in a wide wire, there must be at least the specified cut number minus 1 cuts not belonging to the cut class.
'distanceWithin f_within
	The distance between the via cuts must be less than this value for the via cuts to be counted.
'distanceMeasureType
	(Virtuoso Layout Suite EXL and higher tiers) This parameter specifies that the within distance should be measured as a euclidian or manhattan. The default is euclidian.
'above | 'below | 'bothAboveBelow
	The wire that is used to determine the number of cuts required. By default, the number of cuts required is determined based on the width of the wider of the two wires. 'above: The number of cuts required is determined based on the width of the wire on the layer above. 'below: The number of cuts required is determined based on the width of the wire on the layer below. 'bothAboveBelow: (Virtuoso Advanced Node for Layout Standard) The number of cuts required is determined based on the width of the narrower of the two wires.
'sameMetalOverlap | 'fullyEnclosed
	The minimum number of cuts required is determined based on the width of the wider wire. 'sameMetalOverlap: (Virtuoso Advanced Node for Layout Standard) The constraint applies only if the overlap between the wires on the layers above and below the cut layer contains the via cuts and partly covers the wider wire. The via cuts need not overlap the wider wire. 'fullyEnclosed: (Virtuoso Advanced Node for Layout Only) All via cuts must be completely inside a wide wire to be counted against the minimum via cut requirement. Type: Boolean
f_default	The number of cuts to be used when no table entry applies.
'otherWidth g_otherWidth
	(Virtuoso Layout Suite EXL and higher tiers) The constraint applies only if the wire width on the other layer is less than the specified value.

Examples

• Example 1: minNumCut with above
• Example 2: minNumCut with bothAboveBelow
• Example 3: minNumCut with sameMetalOverlap
• Example 4: minNumCut with fullyEnclosed

Example 1: minNumCut with above

The width of the wire on the layer above determines the number of cuts that a via must contain.

• Width >= 0.1; via cuts = 1
• Width >= 0.3; via cuts = 2
• Width >= 0.5; via cuts = 4
• Width >= 0.6; via cuts = 6
  
  

Example 2: minNumCut with bothAboveBelow

The width of the wires on the layers above and below determine the number of cuts that a via must contain.

• Width >= 0.1; via cuts = 1
• Width >= 0.3; via cuts = 2
• Width >= 0.5; via cuts = 4
• Width >= 0.6; via cuts = 6
  
  

Example 3: minNumCut with sameMetalOverlap

The width of the wider wire determines the number of cuts that a via must contain.

• Width >= 0.0; via cuts = 1
• Width >= 0.2; via cuts = 2

The via is contained in the overlap of the two wires, and this overlap partly covers the wider of the two wires.

Example 4: minNumCut with fullyEnclosed

The width of the wider wire determines the number of cuts that a via must contain.

• Width >= 0.0; via cuts = 1
• Width >= 0.1; via cuts = 2
• Width >= 0.2; via cuts = 3

All via cuts must be fully enclosed by the wide wire.

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