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AR# 4136

12.1 Constraints - How do I initialize the contents of a RAM primitive via a constraint file?


Is it possible to specify the initial contents of a Virtex RAM via a constraint file?


Yes. To specify the contents of a RAM, you must know the instance name(s) of the RAM.
Use the following line in the UCF/NCF file. Note that the NCF file must have the same root name as the input netlist (e.g., if the input netlist name was "design.edf", then the NCF file must be named "design.ncf"):
INST instname INIT = value;
where "instname" is the instance name of the RAM. This must be a RAM primitive, enclosed in quotes. The "value" is a hexadecimal number.
For example, if the instance name of a RAM32X1S is U1, the contents of U1 could be set in the NCF file by placing the following line in a NCF file:
The Constraints Editor is also available for creating the INIT strings.
AR# 4136
Date 12/15/2012
Status Active
Type General Article