Switch units, mils to mm, inaccuracies.

You have to understand what you are doing when you change units. In OrCAD/Allegro when you change the units from mils to mm (for example) you are actually changing the design units. So any values are multiplied / divided by the conversion number 25.4 so the value is changed. For example 10 mils equals 0.254mm. The tool warns you when you make these changes stating that you MUST allow enough decimal places for the changes to be made accurately. If you do not you can get rounding inaccuracies. Pads has an underlying database unit that doesn't get affected by you switching between units (so they round accordingly to suit). Would you prefer a system that made adjustments without your knowledge or a system that told you accurately the state of your design ? I know which I'd prefer. It’s far better to deal with potential DRCs prior to releasing the product than to pay for fabrication of boards that are of no use. Cadence have written a couple of solutions on this very subject. Take a look at:- http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:ViewSolution;solutionNumber=11047568;searchHash=b2fc02c43c33789cf1b8edcdf3facd18 and http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:DocumentViewer;src=wp;q=ApplicationNotes/Silicon-Package-Board_Co-Design/AllegroDesignAcc.pdf

Hi Steve,

i have see in the web many of your video training for OrCAD/Allegro pcb. Thank you very much for your reply and for info, now i read it accurately.

The local Cadence Partner, tell the same you have wrote.

In the past i have used Cadstar then PADS, now i use OrCAD PCB Designer Professional, hope in future to use Allegro. With older pcb tools, no problems to switch to different units ! Is not a problem for generate gerber o manufacturing data with necessary approximation directly from tools.

OrCAD/Allegro are accurate data-base ? Yes i think ! But why cannot easy switch different units ? My request is only for expand the usability of this tool.

Thanks again, Gianni.

Please let me know if this workaround are possible, for easy switch units, at any time ! Starting a new pcb design with SETTING a SPECIFIC BASIC UNIT, with 2-4 decimal places of accuracy, for example: MILS with 2 deicmal places of accuracy. Then when i switch in MILLIMETERS, the system NOT switch really in mm, but CONVERT only the same BASIC UNIT. In this mode the system use a SPECIFIC unit SELECTED from user, BUT NO PROBLEM to switch the values on other unit, because the converted values, are made from the same BASIC value. Please Cadence FIX IT ! Any reply are welcome. Best regards Gianni.

Please solve the switch to mils/mm and viceversa, without inaccuracies !

Best Regards, Gianni.

Talking with ex Zuken user(now Cadence user). The switch units easy at any time are most important !

The competitors tell about this:

Please Cadence solve this !

Best regards, Gianni.