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nc pins

masamasa

hello

 

i have many nc pins (non connect pins) on the design that someone made.

 

many of those nc pins are connected to gnd physically but the design shows no error.

 

is there a way to show an error where nc pins are connected to gnd or some other nets?

 

regards

masa

  • 0

    These pin are net connected to GND in netlist BUT connected physically on pcb?

    Check:

    - DRC mode for spacing

    - DRC setup (-1 indicate no check for spacing)

    - properties on pins (NO_DRC property...)

    verry dangerous this board

  • +1 in reply to JCTEYSSIER0

    I wrote a simple Allegro SKILL check routine shown below:

    <<<

    procedure((Check_Nc_Pins)
    let((net_cnt err_cnt Fp Class SubClass)
    (net_cnt = 0)
    (err_cnt = 0)
    foreach(net ((axlDBGetDesign)->nets)
    net_cnt++
    foreach(branch (net->branches)
    foreach(child (branch->children)
    if((child->objType) then
    if(((child->objType) == "pin") then
    (Fp = car(child->functionPins))
    when((Fp->use == "NC")
    err_cnt++
    (SubClass = cadr(parseString(car(child->startEnd) "/")))
    (Class = upperCase(sprintf(nil "DRC ERROR CLASS/%s" SubClass)))
    (SubClass = sprintf(nil "NC_pin on %s" net->name))
    (axlDBCreateExternalDRC SubClass (child->xy) Class child nil nil)
    )
    )
    )
    )
    )
    )
    (axlMsgPut "%d nets processed, %d DRC flags added" net_cnt err_cnt)
    )
    )

    >>>>

    Below is the journal file entry when running it:

    \i (00:00:29) skill Check_Nc_Pins
    \t (00:00:29) 565 nets processed, 5 DRC flags added
       (00:00:29) t
    \i (00:00:46) browse drcs

  • 0

    Hi Masa,

    If you connect a pin that has no net name to an object that contains another net then a DRC will be produced visually. If you connect a pin that has no net name (Dummy Net) to a dynamic shape then the shape will clear around the pin.

    I suggest that you check your DRC Pin spacing modes and verify pin to shape etc is enabled. Go to Setup > Constraints > Modes to verify DRC Rules.

    Best Regards.

  • 0 in reply to DavidJHutchins

    thank u for ur response, david.

     

    i get 0 drc flags added for nc pins that r connected to gnd.

     

     

    does this skill work if the gnd shape is static?

      

    below shows a partical design of mine and the gnd shape is static in red and the pins in blue have a dummy net.

     

    i do not know how cadence defines nc pins.

     

     

    regards

    masa

  • 0 in reply to excellon1

    Hi Masa,

    The skill code looks for pins with the pinuse value of 'NC'

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