Changing reference designators without re-placing components

Go to file --.export palcement,generate a placement file ,open that file in excel replace old designators with new one and then import new placemant file after reloading the new netlist

Hope it works

Regards

Nayyier 

Hello,

I am assuming that you have 5 schematics and layouts which are being combined during fabrication to
form one PCB which is Assembled as one unit.  This means your reference designators are unique
across all of the different sections (layouts) on the main (combined) PCB.  Now you are looking to
update the layout and schematic so there is no gaps in the Reference Designator numbering when the
boards are assembled individually.

You have a couple of options:

 Option A
   Don't change the Reference Designators on the schematics but use Auto Rename in Allegro to rename
   the Reference Designators so there are no gaps in the numbering then back annotate the updated
   Reference Designators to the schematic.

   Here are the steps:
      1) Logic > Auto Rename RefDes > Rename, check Rename all components and click the MORE button.
      2) Clear the Top and Bottom Layer Identifier, Skip Character(s) then check Preserve current prefixes
      3) Click the CLOSE button on the Rename Ref Des Set Up form.
      4) Click the RENAME button on the Rename RefDes form.

         - This will rename the components so there are no gaps in the reference designators numbering.
         - Now you can back annotate the rename to the schematic and you are good to go.

 Option B
   If you prefer to make the changes on the schematic, just keep track of the Reference Designators
   FROM->TO and generate a text file "was-is_board1.txt" with column 1 being the OLD RefDes and column 2
   being the NEW RefDes as follows:
        U5     U1
        U6     U2

   This "was-is_board1.txt" text file can be used to rename the board prior to importing the single
   board netlist using the batch command REFTXT. Here is the command syntax that can be executed at
   a DOS Prompt as follows:
      reftext was-is_board1.txt combined_board.brd rename_board1.brd

         - This will rename the components based on the "was-is_board1.txt" text file
         - Once complete you can import the single board netlist.
  
Hope this helps,
Mike Catrambone

 Syntax error in command...

Command is:

reftxt was-is_board1.txt combined_board.brd rename_board1.brd

Not:

 reftext was-is_board1.txt combined_board.brd rename_board1.brd