Schematic Syntax

Libraries GuideChapter 12: Attributes, Constraints, and Carry Logic

Schematic Syntax

This section describes how to place attributes on symbols on a schematic. The following guidelines are for specifying locations.

To specify a single location, use the following syntax.

attribute=location
To specify multiple locations, use the following syntax.

attribute=location,location,location

A comma separates locations in a list of locations. (Spaces are ignored if entered.)

When you specify a list of locations, PAR (Place and Route) chooses any one of the listed locations.
To define a range by specifying the two corners of a bounding box, use the following syntax.

attribute=location:location [SOFT]

A colon is only used to separate the corners of a bounding box. The logic represented by the symbol is placed somewhere inside the bounding box. If SOFT is specified, PAR may place the attribute elsewhere to obtain better results.

Following are some examples of location attributes.

LOC=CLB_R1C2	Locates the element in the CLB in the first row, second column
LOC=CLB_R1C2.LC3	Locates the element in the top-most slice of the four slices of the XC5200 CLB located in the first row, second column (XC5200)
LOC=CLB_R1C2.S1	Locates the element in the right-most slice of the two slices of the Virtex or Spartan2 CLB located in the first row, second column
LOC=P12	Assigns the signal to the pin P12
RLOC=R4C4	Assigns the location relative to other elements in the set to row 4, column 4
RLOC=R0Cl.FFX	Assigns the location relative to other elements in the set to the X flip-flop in row 0, column 1
RLOC=R2C3.LC0	Assigns the location of the element to be one slice below another element in the set that has an RLOC=R2C3.LC1 attribute (XC5200)
RLOC=R2C3.S0	Assigns the location of the element to be the right-most slice of another element in the set that has an RLOC=R2C3.S1 attribute (Spartan2, Virtex)
RLOC_ORIGIN=R4C4	Fixes the reference CLB of a designated set at row 4, column 4
RLOC_RANGE=R4C4 : R10C10	Limits the members of a designated set to a range between row 4, column 4 and row 10, column 10

A name can be composed of any ASCII character except for control characters and characters that have special meanings.

Control characters are : (colon) ; (semi-colon) , (comma) and “(double quotes).

Characters with special meaning are / (forward slash) used as the hierarchy separator and . (period) used as the pin separator and for extensions.

For additional propagation rules for each constraint and attribute, refer to the “Macro and Net Propagation Rules” table in the "Attributes/Logical Constraints" section.