3.1.27.6. create_generated_clock (::quartus::sdc)

Intel® Quartus® Prime Pro Edition User Guide: Scripting

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Date 12/13/2021

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3.1.27.6. create_generated_clock (::quartus::sdc)

The following table displays information for the create_generated_clock Tcl command:

Tcl Package and Version	Belongs to ::quartus::sdc
Syntax	`create_generated_clock [-h \| -help] [-long_help]` `[-add]` `[-divide_by` <factor> `]` `[-duty_cycle` <percent> `]` `[-edge_shift` <shift_list> `]` `[-edges` <edge_list> `]` `[-invert]` `[-master_clock` <clock> `]` `[-multiply_by` <factor> `]` `[-name` <clock_name> `]` `[-offset` <time> `]` `[-phase` <degrees> `]` `[-source` <clock_source> `]` `[` <targets> `]`
Arguments	`-h \| -help`		Short help
	`-long_help`		Long help with examples and possible return values
	`-add`		Add clock to existing clock node
	`-divide_by` <factor>		Division factor
	`-duty_cycle` <percent>		Specifies the duty cycle as a percentage of the clock period--accepts floating point values
	`-edge_shift` <shift_list>		List of edge shifts
	`-edges` <edge_list>		List of edge values
	`-invert`		Invert the clock waveform
	`-master_clock` <clock>		Specifies clock of the source node
	`-multiply_by` <factor>		Multiplication factor
	`-name` <clock_name>		Name of generated clock
	`-offset` <time>		Specifies the offset as an absolute time shift
	`-phase` <degrees>		Specifies the phase shift in degrees
	`-source` <clock_source>		Source node for the generated clock
	<targets>		List or collection of targets
Description	Defines an internally generated clock. If -name is not specified, the clock name is the same as the first target in the list or collection. The clock name is used to refer to the clock in other commands. If a clock with the same name is already assigned to a given target, the create_generated_clock command overwrites the existing clock. If a clock with a different name exists on the given target, the create_generated_clock command is ignored unless the -add option is used. The -add option can be used to assign multiple clocks to a pin or port, and is recommended be used with -master_clock option. The source of the generated clock, specified by -source, is a port, pin, register, or net in the design. All waveform modifications are relative to this point. If more than one clock feeds the source node, the -master_clock option must be used to specify which clock to modify. The source latency of the generated clock is based on the clock network of the generated clock, and not the clock network of the node specified using -source. This latency is added to any source latency of the master clock. If no target is specified, the clock is treated as a virtual clock. In that case, the source latency of the generated clock will be equal to the source latency of the master clock, plus any added latency specified with set_clock_latency. The -divide_by, -multiply_by, -invert, -duty_cycle, -edges, and -edge_shift options modify the waveform relative to the waveform at the source node. Clock division and multiplication, using -divide_by and -multiply_by, is performed relative to the first rising edge. Clock division is based on edges in the master clock waveform, and scaled if the division is an odd number. Use the -duty_cycle option to specify the new duty cycle for clock multiplication. Use the -phase option to specify any phase shift relative to the new clock period. Use the -offset option to specify an arbitrary offset or time shift. Use the -invert option to invert the generated waveform. The -phase and -duty_cycle options may be specified as a decimal value (e.g. 22.5) or as a ratio of two numbers (e.g. 45/2). The latter form may improve Timing Analyzer accuracy when detecting relationships between related clocks. Clock generation can also be specified with the -edges and -edge_shift options. The -edges option accepts a list of three numbers specifying the master clock edges to use for the first rising edge, the next falling edge, and next rising edge. Edges of the master clock are labeled according to the first rising edge (1), next falling edge (2), next rising edge (3), etc. For example, a basic clock divider can be specified equivalently with -divide_by 2 or -edges {1 3 5}. The -edge_shift option accepts a list of three time values, the amount to shift each of the three edges. The value of the targets is either a collection or a Tcl list of wildcards used to create a collection of the appropriate type. The values used must follow standard Tcl or Timing Analyzer-extension substitution rules. See the help for use_timing_analyzer_style_escaping for details.
Example Usage	# Create a clock and a divide-by-2 generated clock create_clock -period 10 [get_ports clk] create_generated_clock -divide_by 2 -source [get_ports clk] -name clkdiv [get_registers clkdiv] # An equivalent generated clock create_generated_clock -edges {1 3 5} -source [get_ports clk] -name clkdiv [get_registers clkdiv] # Specify a clock multipler with a 60% duty cycle create_generated_clock -multiply_by 2 -source [get_ports clk] -duty_cycle 60 [get_pins clkmult\|combout] # Specify an inverted divide-by-2 clock relative to the output of the source clock create_generated_clock -divide_by 2 -invert -source [get_ports clk] -name nclkdiv [get_registers clkdiv] # Specify a divide-by-2 clock with a 90-degree phase shift create_generated_clock -divide_by 2 -phase 90 -source [get_ports clk] -name clkdiv [get_registers clkdiv] # Create a divide-by-2 generated clock generated off the falling edge of the source clock create_generated_clock -edges {2 4 6} -source [get_ports clk] -name clkfall_div [get_registers clkfall_div] # Assign two clocks to an input port that are switched externally, # along with an internal clock divider. create_clock -period 10 -name clk100Mhz [get_ports clk] create_clock -period 6.667 -name clk150Mhz -add [get_ports clk] create_generated_clock -divide_by 2 -name clk50Mhz -source [get_ports clk] -master_clock clk100Mhz -add [get_registers clkdiv] create_generated_clock -divide_by 2 -name clk75Mhz -source [get_ports clk] -master_clock clk150Mhz -add [get_registers clkdiv] # Create a virtual clock, and two generated clocks that derive from it. # This makes the generated clocks related, so crossings between them are not asynchronous. create_clock -period 10 -name virtual_base create_generated_clock -master_clock virtual_base -divide_by 2 [get_ports clka] create_generated_clock -master_clock virtual_base -divide_by 4 [get_ports clkb]
Return Value	Code Name	Code	String Return
	TCL_OK	0	INFO: Operation successful
	TCL_ERROR	1	ERROR: Timing netlist does not exist. Use create_timing_netlist to create a timing netlist.

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Intel® Quartus® Prime Pro Edition User Guide: Scripting

3.1.27.6. create_generated_clock (::quartus::sdc)