Prevent Inferrance of Megafunctions

[Altera_Forum]

Hello, 

 I have a large shift-register that is being optimized by the synthesizer into a megafunction equivalent. The problem is, I need this register to stay a register (DFFs).  Is there a way to turn-off this optimization?  Thanks!

[Altera_Forum]

yes. 

 go assignments -> settings -> analysis and synthesis settings -> more settings  There is a setting called "auto shift register placements". Change this to "off".  be wary though - these are global settings. I think these settings can be assigned to individual entites via assignments.

[Altera_Forum]

Right click on the hierarchy and Locate -> Assignment Editor. Copy and paste the name from the top filter bar to the To column. Auto Shift Register Replacement is the assignment again.

[Altera_Forum]

The global assignment worked - but trying to assign this rule to a specific part of the design did not. 

 I found the collection of registers that I need to apply the rule to via the drop-down menu in the 'To' textbox. I filtered on 'Registers: pre-synthesis' and added the name this way.  The collection always has a question mark by it, and the tooltip says that the name is not recognized (which seems odd, because I got the name from the drop-down list).  I've uploaded an image of this to google docs for reference:  https://docs.google.com/open?id=0b4wyejzmihtnzmnkued6aevhrnc  Any ideas?  Thanks!

[Altera_Forum]

It's possible by synthesis attributes, as discussed in a different thread http://www.alteraforum.com/forum/showthread.php?p=155649 

 reg data = 6000'b0 /* synthesis altera_attribute = "-name AUTO_SHIFT_REGISTER_RECOGNITION OFF" */;