Constraints Editor
Initializing Block RAM
You can use the Block RAM Initialization dialog box to initialize block RAM. This sets the initial logic state for the specified address or addresses. This constraint and its values are architecture specific, and appropriate checks are applied to values depending on the architecture.
Use the INIT constraint sparingly. Initialization should be handled as part of the HDL code whenever possible.
To Initialize Block RAM
  1.  Open the Block RAM Initialization dialog box.
  2.  To limit the block RAM listed in the Block RAM list, enter a filter string in the Filter box and click Find. For example, to list only block RAM containing the string "listb," type *listb* in the Filter box. The filter is not case sensitive.
  3.  From the Block RAM list, select the block RAM to initialize.
  4.  In the Comment box, enter a comment for this initialization entry.
  5.  To initialize a single address, click Single Address. To initialize a range of addresses, click Address Range.
  6.  In the Starting Address box, enter the single address to initialize or the starting address of the range to initialize.
  7.  In the Ending Address box, enter the last address of the range to initialize. This box is only visible if you selected to set a range of addresses.
  8.  In the Initialization Value box, enter the initial value to be stored in the specified address or addresses.
  9.  In the Parity Value box, enter the parity value for the selected block RAM.
Initializing block RAM creates an INIT constraint. The new constraint appears in the current Workspace table.
For more information about this constraint, see the Constraints Guide in the online document collection.
See Also

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