About GCF files

You can define the following types of constraints in a GCF constraint file:

Note: Only ProASIC devices support GCF Timing commands. All other GCF commands are supported by both ProASIC and ProASICPLUS devices. Use the SDC timing commands to import timing constraints for ProASICPLUS devices.

Designer supports the following GCF commands.

GCF Timing Commands	Action
create_clock	Creates a clock and defines its period and waveform
generate_paths	Modifies the way Designer generates internal path constraints for the placer to do timing-driven placement
set_false_path	Defines false paths in the design; false paths are not considered in the timing driven place-and-route system
set_input_to_register_delay	Defines the timing budget for incoming signals to reach a register
set_max_path_delay	Constrains the maximum delay on paths
set_multicycle_path	Defines how many clock cycles a signal has to travel through these paths
set_register_to_output_delay	Defines the timing budget for outgoing signals to be clocked out
GCF Placement Commands	Action
net_critical_ports	Specifies a specific subset of critical ports on a net
set_critical	Specifies critical nets and their relative criticality over other critical nets.
set_critical_port	Identifies design I/O ports that have above-normal criticality
set_empty_io	Specifies a location in which no I/O pin should be placed
set_empty_location	Specifies a location in which no cell should be placed
set_initial_io	Initially assigns package pins to I/O ports or sets the location of I/O ports
set_initial_location	Initially sets the location of a cell instance at specified x, y coordinates
set_io	Either assigns package pins to I/O ports or sets the location of I/O ports at a specified location on a device
set_io_region	Places specific I/O instances into a target rectangular region
set_location	Assigns a cell instance to the specified x,y coordinates
set_memory_region	Creates and assigns memory to a region
set_net_region	Places all the connected instances, driver, and all the driven instances for the net(s) into the specified rectangle
Global Resource Commands	Action
dont_fix_globals	Disables the default action that automatically corrects the choice of global assignment to use only the highest fanout nets
read	Specifies the name of the constraint file containing the constraints to use
set_auto_global	Specifies the maximum number of global resources to use
set_auto_global_fanout	Sets the minimum fan-out a net must have to be considered for automatic promotion to a global
set_global	Classifies the specified nets as global nets
set_noglobal	Classifies nets to avoid automatic promotion to global nets
use_global	Specifies a single spine (LocalClock) or a rectangle of spine region which may encompass more than one spine region

Netlist Optimization Commands	Action
dont_optimize	Removes buffers or inverters from the netlist
dont_touch	Enables you to selectively disable optimization of named hierarchical instances
optimize	Turns on all netlist optimizations (the default mode
set_max_fanout	Sets the maximum fan-out limit on the specified nets when optimizing buffers and inverters

About GCF files

See Also