Appendix A

UCF Syntax

This appendix describes the UCF syntax for constraints created with the Constraints Editor. It contains the following sections.

• “Groups by Element (Timegrp)”
  
  
• “Groups by Nets (TNM)”
  
  
• “Timing THRU Points (TPTHRU)”
  
  
• “Pad to Setup”
  
  
• “Clock to Pad”
  
  
• “Slow/Fast Path Exceptions (FROM TO)”
  
  
• “Multicycle Paths (FROM/THRU/ TO)”
  
  
• “False Paths (FROM TO TIG)”
  
  
• “False Paths by Net (Net TIG)”
  
  
• “Period”
  
  
• “Location”
  
  
• “Prohibit I/O Locations”
  
  

Groups by Element (Timegrp)

Specifies a new group in terms of instances (FFS, PADS, RAMS or LATCHES).

TIMEGRP identifier= group_name_1 : group_name_2 ...

TIMEGRP identifier= element(out_net)

where:

identifier is the name for the new time group.

group_name_1 and group_name_2 are predefined time groups.

element is FFS, PADS, RAMS or LATCHES.

out_net is the output net of the element.

Groups by Nets (TNM)

Identifies the elements that make up a group which can then be used in a timing specification. A TNM (pronounced tee-name) is a flag that you place directly on your schematic to tag a specific net, element pin, primitive or macro. All symbols tagged with the TNM identifier are considered a group.

INST instance_name TNM=identifier

NET net_name TNM=identifier

where:

instance_name is the name of a pad, RAM, flip-flop, or latch.

identifier is a value that consists of any combination of letters, numbers, or underscores. Keep it short for convenience and clarity.

net_name is the name of a clock net.

Timing THRU Points (TPTHRU)

Identifies an intermediate point on a path.

INST instance_name TPTHRU=identifier

NET net_name TPTHRU=identifier

where:

identifier is a unique name.

Pad to Setup

Specifies the timing relationship between an external clock and data at the pins of a device. Operates on pads or predefined groups of pads.

TIMEGRP padnet_name OFFSET=IN time unit BEFORE clocknet_name [TIMEGRP reg_group]

TIMEGRP padgroup_name OFFSET=IN time unit BEFORE clocknet_name [TIMEGRP reg_group]

OFFSET IN time unit BEFORE

where:

padgroup_name is the name of a group of pads predefined by the user.

reg_group_name is the name of a group of registers predefined by the user.

For more information on Pad to Setup, see the “From the Global Tab Window” section in the "Using the Constraints Editor" chapter.

Clock to Pad

Specifies the timing relationship between an external clock and data at the pins of a device. Operates on pads or predefined groups of pads.

TIMEGRP padnet_name OFFSET=OUT time unit AFTER clocknet_name [TIMEGRP reg_group]

TIMEGRP padgroup_name OFFSET=OUT time unit AFTER clocknet_name [TIMEGRP reg_group_name]

OFFSET OUT time unit AFTER

where:

padgroup_name is the name of a group of pads predefined by the user.

reg_group_name is the name of a group of registers predefined by the user.

For more information on Clock to Pad, see the “From the Global Tab Window” section in the "Using the Constraints Editor" chapter.

Slow/Fast Path Exceptions (FROM TO)

Establishes an explicit maximum acceptable time delay between groups of elements.

TIMESPEC tsid=FROM source_group time [unit]

TIMESPEC tsid=FROM source_group TO destination_group time [unit]

TIMESPEC tsid=FROM source_group THRU timing point(s) time [unit]

TIMESPEC tsid=FROM source_group THRU timing_point(s) TO destination_group time [unit]

THRU timing_point(s) TO destination_group time [unit]

TO destination_group time [unit]

where:

source_group and destination_group are FFS, RAMS, PADS, or LATCHES, as selected by the user.

timing point(s) are intermediate points as specified by the TPTHRU Points constraint on the Advanced tab window.

Multicycle Paths (FROM/THRU/ TO)

Establishes a maximum acceptable time delay between groups of elements relative to another timing specification.

TIMESPEC tsid=FROM source_group time [unit]

TIMESPEC tsid=FROM source_group TO destination_group time [unit]

TIMESPEC tsid=FROM source_group THRU timing point(s) time [unit]

TIMESPEC tsid=FROM source_group THRU timing_point(s) TO destination_group time [unit]

THRU timing_point(s) TO destination_group time [unit]

TO destination_group time [unit]

where:

source_group and destination_group are FFS, RAMS, PADS, or LATCHES, as selected by the user.

timing point(s) are intermediate points as specified by the TPTHRU Points constraint on the Advanced tab window.

False Paths (FROM TO TIG)

Marks paths between a source group and a destination group that are to be ignored for timing purposes.

NET net_name TIG

False Paths by Net (Net TIG)

Marks nets that are to be ignored for timing purposes.

NET net_name TIG

Period

Defines a clock period.

TIMESPEC tsid=PERIOD clocknet_name | timegroup_name time [unit] [HIGH | LOW high_or_low_time unit]

where:

where id is a unique identifier. The identifier can consist of letters, numbers, or the underscore character (_).

unit is picoseconds, nanoseconds, microseconds, or milliseconds.

HIGH | LOW indicates the high or low state of the first pulse of the wave form.

Location

Locks a user-defined port to a device pin.

LOC=location

where:

location is a device pin identification; for example, A10.

Prohibit I/O Locations

Disallows the use of an I/O site by PAR (Place and Route) and EPIC (Editor for Programmable Integrated Circuits).

CONFIG PROHIBIT=location1, [location2..., locationn]

where

location1, location2, and locationn are I/O sites.