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AR# 37628

Place - ERROR:Place:1023 - Unroutable Placement


I am receiving the following error:

ERROR:Place:1023 - Unroutable Placement! A global clock component <my_bufg_1> configured as a selectable mux is placed in site BUFGMUX_X3Y5.
This configuration requires that the global clock site BUFGMUX_X3Y6 either be empty or contain a global buffer or mux with the inputs IN0 and IN1 either not driven by a signal or driven by the same signals as the original muxes IN1 and IN0 pins respectively in order to route up both of the inputs.
In other words the input signal for IN0 on one buffer must be the same as the input signal driving IN1 on the other buffer (or one of them must not be driven) to place the two buffers in the paired sites.
The site BUFGMUX_X3Y6 has the global buffer <my_bufg_2> placed there. This design is unroutable.


The problem is that paired BUFGMUX locations share routing resources to reach the I0/I1 input pins.

I0 of one buffer shares a routing resource with I1 of the other and vice versa.

Because of this, if both inputs of a BUFGCTRL are used then the neighboring BUFGCTRL in the pair must have compatible connectivity or there will be an unroutable connection.
See UG382 for more information:
AR# 37628
Date Created 08/24/2010
Last Updated 11/23/2016
Status Active
Type General Article
  • Spartan-6