Update clock routing on global clocks if they are modified after placement
Syntax
update_clock_routing [‑quiet] [‑verbose]Usage
| Name | Description |
|---|---|
[-quiet]
|
Ignore command errors |
[-verbose]
|
Suspend message limits during command execution |
Categories
Description
The update_clock_routing command is an advanced command used for manually updating the routing structures of all global clocks in designs targeting the UltraScale architecture. The command operates on all global clocks in a design, not individual clocks.
Due to a more flexible clocking architecture, UltraScale and UltraScale+ designs require a two-step process for routing global clocks. First the Vivado placer assigns the routing resources required to route the global clocks from the clock source to the destination clock regions (CLOCK_ROOT or USER_CLOCK_ROOT). Next the Vivado router fills in the routing gaps on the clock nets. In between these two steps the resulting structures are called gap trees: each global clock net has its base routing resources assigned but with large routing gaps where no routing resources have been assigned.
After gap trees are constructed, the router optimally routes the remaining clock network to all leaf-level primitives to fill in the routing gaps. During an implementation run the global clock routing is handled automatically. However in cases where the clock tree has been changed after implementation, by modifying the USER_CLOCK_ROOT property on a clock net for instance, the Vivado tool may need the update_clock_routing command to properly rebuild the gap trees and fill in the routing gaps.
- Moving the clock root of a global clock.
- Adding or moving loads of a global clock into a clock region not yet occupied by the global clock, then running timing analysis on the updated design.
Arguments
-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.
-verbose - (Optional) Temporarily override any message limits and return all messages from this command.
set_msg_config command.Examples
set_property USER_CLOCK_ROOT X1Y0 [get_nets {clk1 clk2}]
route_design -unroute -nets [get_nets {clk1 clk2}]
update_clock_routing