Issues with pin connectivity in Layout

I just tried this - it should work. However, there are some provisos which probably depend on the physical verification tool you're using.

I had the two VDD pins that I wanted to be must connect. I then used Connectivity->Pins->Must Connect and then followed the instructions - first I selected one of the two pins (to get the net information) and then at the next prompt selected both pins (I clicked on one and then shift click the other). In the navigator it did indeed show one of the terminals as renamed to mustConnect_1_VDD - that's what I'd expect. I didn't get the marker you mentioned. Using Connectivity->Pins->Pin Connectivity Setting showed the grouping too. 

I can't really see how that would happen - it suggests that it's got a must join attribute to a shape rather than a pin figure.

It's correct that the terminal would be renamed (and the net) - this is because when you have a must connect, they're not actually joined inside and so they're implemented as separate nets. The must join attribute tells the level above that it needs connecting.

Can you try running this code:

procedure(abPinInfo(@optional (cellView geGetEditCellView()))
  foreach(term cellView~>terminals
    printf("TERM %L NAME %L MUSTJOIN %L PHYSONLY %L\n" term term~>name term~>mustJoinTerms term~>physOnly)
    foreach(pin term~>pins
      printf(" PIN %L NAME %L\n" pin pin~>name)
      foreach(fig pin~>figs
        printf(" LAYER %L CENTER %L\n" fig~>lpp centerBox(fig~>bBox))
      )
    )
  )
  t
)

Load it and then just call abPinInfo() with the window current.

Also, which subversion of Virtuoso are you using? Type getVersion(t) in the CIW to find out (or it's on the Help->About window).

There should be no need to change the schematic to support this.

Note that for LVS, it may not know about the connectivity attribute unless it's working from the OA database. Often you have to tell LVS tools about virtual connections in other ways (the common convention from Dracula days which has been carried forward into many tools is to label the "pin" with a name that ends in a colon (e.g. "VDD:") to indicate this virtual connection). You didn't mention which LVS tool you're using, so can't really be sure what the issue might be there.

Regards,

Andrew.

Hi Andrew,

First off, apologies for any missing info. I only have started recently to use Virtuoso, so I'm still learning a number of things about it.

> It's correct that the terminal would be renamed (and the net)

I see the net change only on the pin properties, but not on other objects that are connected to it. Is that the correct behavior?

> Also, which subversion of Virtuoso are you using?

getVersion returns: sub-version  IC6.1.6-64b.500.8

I tried running your code. What I get is the following:

abPinInfo()
TERM db:0x1611db9a NAME "nI0" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b29a NAME "nI0"
LAYER ("metal1" "drawing") CENTER (10.85 10.01)
TERM db:0x1611db9b NAME "nI1" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b29b NAME "nI1"
LAYER ("metal1" "drawing") CENTER (10.26 10.36)
TERM db:0x1611db9c NAME "nI2" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b29c NAME "nI2"
LAYER ("metal1" "drawing") CENTER (8.68 10.36)
TERM db:0x1611db9d NAME "nI3" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b29d NAME "nI3"
LAYER ("metal1" "drawing") CENTER (7.1 10.36)
TERM db:0x1611db9e NAME "nI4" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b29e NAME "nI4"
LAYER ("metal1" "drawing") CENTER (5.52 10.36)
TERM db:0x1611db9f NAME "nI5" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b29f NAME "nI5"
LAYER ("metal1" "drawing") CENTER (3.94 10.36)
TERM db:0x1611dba0 NAME "nI6" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b2a0 NAME "nI6"
LAYER ("metal1" "drawing") CENTER (2.36 10.36)
TERM db:0x1611dba1 NAME "nI7" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b2a1 NAME "nI7"
LAYER ("metal1" "drawing") CENTER (0.78 10.36)
TERM db:0x1611dba2 NAME "nOUT0" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b2a2 NAME "nOUT0"
LAYER ("metal1" "drawing") CENTER (14.39 7.7)
TERM db:0x1611dba3 NAME "nOUT1" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b2a3 NAME "nOUT1"
LAYER ("metal1" "drawing") CENTER (12.99 7.7)
TERM db:0x1611dba4 NAME "nOUT2" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b2a4 NAME "nOUT2"
LAYER ("metal1" "drawing") CENTER (12.35 7.7)
TERM db:0x1611dba5 NAME "GND" MUSTJOIN nil PHYSONLY nil
PIN db:0x26d1b2a5 NAME "P__11"
LAYER ("metal1" "drawing") CENTER (7.49 4.07)
TERM db:0x1611dba6 NAME "mustConnect_1_VDD" MUSTJOIN (db:0x1611dba7) PHYSONLY nil
PIN db:0x26d1b2a7 NAME "P__13"
LAYER ("metal1" "drawing") CENTER (15.1 1.515)
TERM db:0x1611dba7 NAME "VDD" MUSTJOIN (db:0x1611dba6) PHYSONLY nil
PIN db:0x26d1b2a6 NAME "P__12"
LAYER ("metal1" "drawing") CENTER (0.12 11.695)
t

> You didn't mention which LVS tool you're using.

We are using Calibre v2013.1_14.11 . Also, I went through the LVS options after reading your comment about colons, and there is indeed an option to virtually connect pins with a common prefix followed by a colon.

So, I tried calling the two pins VDD:0 and VDD:1, setting them as must connect, and enabling the virtual connect option on Calibre. If I do that, the LVS report comes out with no errors; however, I get short-circuit markers between the pins and the other objects (says there is a short between e.g. VDD and VDD:0).

More importantly, if I then place the symbol of the cell I'm creating in a new schematic and try to make a layout of it, the connection to the VDD pin on the schematic no longer carries through to the layout. (That is, on the layout, if I start a path from the VDD:0 pin and then check its properties, the net name property is blank)

Thanks for your help,

Dave