Converting CAD XY Coordinates for Bottom Side SMT Assembly in Allegro or Other Tools

As you know, CAD systems will report the component centroid location and rotation looking through the board, but not turning the board over. Our internal assembly house wants engineering to give them the coordinates as if they are turning the board over.

So, if my original datum (0,0) is the left bottom corner of the board, they will turn the board over. Now the original datum would be on the right bottom corner, but they still use on the left bottom corner of the board in the smt machine, and they do a subtraction in the x-direction to get the correct coordinate.

The only reason that they change the datum when they turn the board over is because all of the coordinates will be positive. Does anyone else run into this predicament? What does other assembly shops industry wide do in your opinion?
Is there a macro, spreadsheet, or script(for Allegro) out there? I have searched and have found nothing. I can create a spreadsheet for it, but just wanted to see what you thought first.

I think if you flip the PCB design in the CAD tool the coordinates will result the way you wish... thus you can generate the fabrication files (gerbers or whatever you use) separately for each side of the board.

PS: I might be wrong, but I just reinstalled my OSs and have yet to install a PCB CAD tool. I will test this the first chance I get.

And the answer is... it depends. Depends on what your assembly house wants. Most that I've dealt with are already used to massaging the data from any format/origin/orientation, but if not, I've done the spreadsheet route too.

OIC, an internal assembly house. That explains it. Total inflexibility because they aren't used to dealing with a variety of customers and data formats. Get out your spreadsheet.

The only other option is if your manager has more influence/clout than the manager of the assembly operation and he can gently explain to them that they should have a process to handle standard Allegro outputs. Explain that they are trusting an important data conversion process to their (in-house) customers; that they will have to explain their requirements to each customer, and that each customer might do the conversion in a non-controlled and slightly different way. All told, its a process that should be handled centrally by the assembler. Good luck with that.

Thanks for the response. I did try and flip my design over in the CAD system, but after I change my datum point my coordinates change, but not the rotations. A 90deg should now be a 270deg, ect...

Gary is right. This is an internal assembly shop that wants to just get data from Engineering and not have to mess with it at all. I will ask our Cadence Allegro support if there is any workaround, but I think that the only answer is to use the spreadsheet option.
I was hoping that somebody had a script or macro that can accomplish this in Allegro, but I do not see a way for me to even come up with one since Allegro is limited here.
Thanks to all,

Bob

In this case I tend to agree with Gary, too. I haven't used Allegro so I can't help you there, but I think you can maybe have a way of importing existing data into a spreadsheet and have the changes automated in the spreadsheet editor... Again I haven't really ever done this so it's just a guess.