get_net_delays - 2022.1 English

Vivado Design Suite Tcl Command Reference Guide (UG835)

Document ID
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2022.1 English

Get the routed or estimated delays in picoseconds on a net from the driver to each load pin.


get_net_delays ‑of_objects <args> [‑regexp] [‑nocase] [‑patterns <arg>]
    [‑filter <arg>] [‑to <args>] [‑interconnect_only] [‑quiet] [‑verbose]




Name Description
-of_objects Get 'net_delay' objects of these types: 'net'.
[-regexp] Patterns are full regular expressions
[-nocase] Perform case-insensitive matching. (valid only when -regexp specified)
[-patterns] Match the 'net_delay' objects against patterns. Default: *
[-filter] Filter list with expression
[-to] Get the delay of the net to the given terminal(s) or port(s).
[-interconnect_only] Include only interconnect delays. The default is to include the intra-site delay.
[-quiet] Ignore command errors
[-verbose] Suspend message limits during command execution


Timing, Netlist, Object


Get delay objects for the specified nets in the current design, from the driver to each load pin, or to specified load pins, through specific pins.

The delay object contains properties defining the maximum and minimum delays for the fast and slow process corners. Use the get_property command to extract the property of interest from the delay object. Delay property values on the delay object are specified in picoseconds.
Tip: In most cases the Vivado® tools return delay values specified in nanoseconds, but the delay object uses picoseconds.

The values returned are calculated or estimated depending upon whether the net is routed. Delay values can include the actual delay of routed interconnect, or estimated net delays for unrouted nets. The net delay can also include delay through logic elements or device sites, or just include the interconnect delay.

Note: To improve memory and performance, the get_* commands return a container list of a single type of objects (e.g. cells, nets, pins, or ports). You can add new objects to the list (using lappend for instance), but you can only add the same type of object that is currently in the list. Adding a different type of object, or string, to the list is not permitted and will result in a Tcl error.

The get_net_delays command returns the delay objects for the specified nets, or returns an error if it fails.


-of_objects <arg> - (Required) Get the net delays of the specified net objects. This option can be used to reduce the amount of data returned by the get_net_delays command.
Note: The -of_objects option requires objects to be specified using the get_* commands, such as get_nets in the case of the get_net_delays command.
-regexp - (Optional) Specifies that the search <patterns> are written as regular expressions. Both search <patterns> and -filter expressions must be written as regular expressions when this argument is used. Xilinx® regular expression Tcl commands are always anchored to the start of the search string. You can add ".*" to the beginning or end of a search string to widen the search to include a substring. See for help with regular expression syntax.
Note: The Tcl built-in command regexp is not anchored, and works as a standard Tcl command. For more information refer to

-nocase - (Optional) Perform case-insensitive matching when a pattern has been specified. This argument applies to the use of -regexp only.

-patterns <arg> - (Optional) Match net_delays against the specified patterns. The default pattern is the wildcard '*' which gets a list of all net_delays in the project. More than one pattern can be specified to find multiple pins based on different search criteria.
Note: You must enclose multiple search patterns in braces, {}, or quotes, "", to present the list as a single element.

-filter <args> - (Optional) Filter the results list with the specified expression. The -filter argument filters the list of objects returned by get_net_delays based on property values on the delay objects. You can find the properties on an object with the report_property or list_property commands. In the case of the delay object, "NET", "FAST_MAX" and "FAST_MIN" are some of the properties that can be used to filter results.

The filter search pattern should be quoted to avoid having to escape special characters. String matching is case-sensitive and is always anchored to the start and to the end of the search string. The wildcard “*” character can be used at the beginning or at the end of a search string to widen the search to include a substring of the property value.
Note: The filter returns an object if a specified property exists on the object, and the specified pattern matches the property value on the object. In the case of the "*" wildcard character, this will match a property with a defined value of "".
For string comparison, the specific operators that can be used in filter expressions are "equal" (==), "not-equal" (!=), "match" (=~), and "not-match" (!~). Numeric comparison operators <, >, <=, and >= can also be used. Multiple filter expressions can be joined by AND and OR (&& and ||). The following gets input pins that do NOT contain the “RESET” substring within their name:
get_pins * -filter {DIRECTION == IN && NAME !~ "*RESET*"}
Boolean (bool) type properties can be directly evaluated in filter expressions as true or not true:

-to <args> - (Optional) Specifies the endpoints of nets for delay calculation. Pin, port, and pip objects can be specified as endpoints.

-interconnect_only - (Optional) Include only interconnect delays to determine the delay on the net due to routing. The default is to also include the intra-site delay into the delay calculation.
Tip: When using get_net_delays to define delay limits for the route_design command -min_delay or -max_delay options, you should use the -interconnect_only option to ensure the specified net delay includes just the interconnect.
-quiet - (Optional) Execute the command quietly, returning no messages from the command. The command also returns TCL_OK regardless of any errors encountered during execution.
Note: Any errors encountered on the command-line, while launching the command, will be returned. Only errors occurring inside the command will be trapped.
-verbose - (Optional) Temporarily override any message limits and return all messages from this command.
Note: Message limits can be defined with the set_msg_config command.


The following example gets the interconnect delay values for the specified net, and returns it in the form of a delay object:
report_property -all [lindex [get_net_delays -interconnect_only \
-of_objects [get_nets control_reg[*]]] 16 ]
Tip: The FAST_MAX, FAST_MIN, SLOW_MAX, and SLOW_MIN properties on the delay object are reported in picoseconds.