Quartus II Settings File Reference Manual - Altera

Chapter 4: Analysis & Synthesis Assignments 4–55
DONT_MERGE_REGISTER
DONT_MERGE_REGISTER
Type
When set to On, this option prevents the specified register from merging with other
registers, and prevents other registers from merging with the specified register.
You can use this option to instruct the Compiler to use the user-specified timing
constraints on the register during synthesis. For example, if the register has a
multicycle constraint, this option prevents the Compiler from merging other registers
into the specified register, avoiding unintended timing and functional effects.
This option is different from Preserve Register logic option because it does not
prevent a register with constant drivers or a redundant register from being removed.
In addition, this option prevents other registers from merging with the specified
register.
This option is ignored if the register does not drive anything or if it has constant
drivers, in which case the register is removed during synthesis.
This option is ignored if it is applied to anything other than a register or a design
entity containing registers.
Boolean
Device Support
This setting can be used in projects targeting any Altera device family.
Notes
This assignment supports wildcards.
Syntax
set_global_assignment -name DONT_MERGE_REGISTER -entity
set_instance_assignment -name DONT_MERGE_REGISTER -to -entity
Example
set_instance_assignment -name dont_merge_register on -to foo
June 2012 Altera Corporation Quartus Settings File
Reference Manual