VXL placing cells/pcells off grid

[Tim]

IC5141 - Solaris

Hi ,

Recently we have been having a problem with VXL placing cells off grid
when performing a "Gen from Source" or "Update Components and Nets". We
have not seen this before on this PDK which has been used on this and
older Cadence versions.

The designer has his layout grid set to 0.05 x 0.05 as a default
".cdsenv" but the cells are being placed on a 0.025 grid.

Has anyone else had this problem or is there another variable that
needs to be set to fix this?

Thanks in Advance,
Tim

 

[vlsidesign]

Tim wrote:

IC5141 - Solaris
Recently we have been having a problem with VXL placing cells off grid
when performing a "Gen from Source" or "Update Components and Nets".

I am just a layout guy ... but for what it's worth, I have not seen
this problem, but I do have problems when I move/flip
("Sideways/UpsideDown" from Move menu) in XL. I think it might have to
do with the data-extents being used (sometimes you have text hanging
off the end), or sometimes when moving vias and paths, the vias do
weird things, not sure why. The workaround I do is to go out of XL
mode, do my move or flip, etc. and then go back into XL.

 

[Tim]

Thanks for the reply!

We were looking into it more this morning and concluded that i could be
happening while rotating with the mouse button during a move. I have
done this numerous times with different VXL version and this is the
first time we are seeing this behavior. We tried doing a "move
relative" from the Move pop-up and it doesn't allow an off grid move.

Another odd thing is that a group of cells were moved and rotated and
only the cells were off grid the metal interconnect polygons stayed on
grid.

Thanks,
Tim

 

[Tim]

I believe we solved the problem. If your layout is hierarcical and you
edit in place into a lower cell and then do a pick from schematic the
cell is placed off grid. The bounding box of the cell to be placed also
shows at the cursor but is placed in a different location.

The move flipped or rotated my also have this problem during edit in
place. I have to look into this next.

Tim

 

[vlsidesign]

Tim wrote:

I believe we solved the problem. If your layout is hierarcical and you
edit in place into a lower cell and then do a pick from schematic the
cell is placed off grid. The bounding box of the cell to be placed also
shows at the cursor but is placed in a different location.

The move flipped or rotated my also have this problem during edit in
place. I have to look into this next.

I'll keep this in mind. Thank you for posting your findings.

 

[vlsidesign]

On Jan 12, 9:57 am, "vlsidesign" <ford...@gmail.com> wrote:

vlsidesign wrote:
snip
... I do have problems when I move/flip
("Sideways/UpsideDown" from Move menu) in XL. I think it might have to
do with the data-extents being used (sometimes you have text hanging
off the end), or sometimes when moving vias and paths, the vias do
weird things, not sure why. The workaround I do is to go out of XL
mode, do my move or flip, etc. and then go back into XL.

By the way, I found out that there is an option on the "Move" popup
menu, called "Constraint Assisted Control", if I select the button
"ignore", I no longer have this offgrid problem, and the misc "weird"
behavior.