How exactly does this physical constraint "Allow" function work?

Question

Hi Team, 
 Good Day!..., 
 
 I couldn't figure out "how this Allow works in physical constraint" because there are multiple drop-down menus, each with a different function. 
 what is mean by Ts and it stands for ?

To better understand the concept, kindly explain in depth with a few examples. 
 
 Thanks in advance..... 
 
 .

aniju · Accepted Answer

its a Pad-to-Pad overlap checks, please see below Pad-Pad conditions. 
 PAD-PAD: 
 Constriant Set to ' Not-Allowed ', if any via are overlaping with pins, it will flag the DRC. 
 
 Constriant Set to ' VIAS_PINS_ONLY ', it means pins and vias are accepatble and won't flag the DRC. 
 
 Constriant Set to ' VIAS_VIAS_ONLY ', It means Via-Via overlap is only acceptable, if via overlaps with pads will flag the DRC, similarly for microvias and pins. 
 
 TS: Ts is a T junctions on subclass of cline segments, here are conditions. 
 Set Ts as Not_Allowed. it means T- junctions are not allowed anywhere in the net but T-junction is present here and flagging the DRC . 
 
 Set Ts as ' PINS_VIAS_ONLY '. it means T-junctions are accepted at Pins or vias. here is the DRC which is outside of PINS and VIAS. 
 
 Set Ts as ' NOT_ALLOWED ' and created the T junction at pins and flagging the DRC . 
 
 Set Ts as ' PINS ONLY ' and created T joint at via and flaging the DRC.

steve · Answer

Pad-Pad Connect = Checks whether a pin/via whose connect point lies within the extents of another pin/via forms a direct connection without the presence of an intermediate cline. You can choose from the available values: 
 ALL_ALLOWED - Specifies that direct connections can form anywhere. VIAS_PINS_ONLY - Specifies that only pin-via and pin microvia direct connections can be formed. VIAS_VIAS_ONLY - Specifies that only via-via and via microvia direct connections can be formed. MICROVIAS_MICROVIAS_ONLY - Specifies that only microvia-microvia direct connections can be formed. MICROVIAS_MICROVIAS_COINCIDENT_ONLY - Specifies that microvia-microvia direct connections can be formed, only if the microvias are co-incident. NOT_ALLOWED - Prohibits direct connections everywhere. Clear - Clears the previous settings. 
 Note: Use for conditions where one or both of the pads, vias, or microvias that should be overlapping or coincident is a surface mount device pad. For example, this allows symbol surface mount device pads to embed associated fan-outs without the need to draw a connect line. 
 The T is whether a T connection is allowed / where it is allowed. A T is a connection of clines that form the letter T (right angled connection). Some users don't allow these others do.

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How exactly does this physical constraint "Allow" function work?

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