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AR# 63976

UltraScale Partial Reconfiguration - "update_design -black_box" causes ERROR [Constraints 18-608] about Conflicting nets


My partial reconfiguration design completes the initial configuration without any routing issues.

However, when executing "update_design -black_box" to carve the reconfigurable module in the routed design, it fails with the following error:

ERROR: [Constraints 18-608] We cannot route the nets within the site SLICE_X32Y113. Reason: Conflicting nets for physical connection RST_EFGHINV_OUT driven by SLICE_X32Y113.RST_EFGHINV.OUT: 1: n_1_cipher, 2: RST_N_IBUF_inst/O

Why does this error occur?


When you run "report_route_status" in the design after carving the reconfigurable module (RM), you can find the unrouted nets.

There are 2 types of unrouted nets:

1) When the net passes through the RM from input to output.

The topological structure is shown as common-driver-multiple-output:

static driver ----------> RM route-through --> static loads 
                          |------> static loads 

2) When the driver within the RM drives out multiple ports to the rest of the design

Such nets create illegal sites when the reconfigurable module gets updated, which causes the routing issue.

In Vivado 2015.1, opt_design is enhanced to insert a buffer LUT1 for both signal nets and pwr/gnd nets at the beginning, which can remove the conflicting nets issue.

AR# 63976
Date 06/15/2017
Status Active
Type General Article
  • Kintex UltraScale
  • Virtex UltraScale
  • Vivado Design Suite - 2014.4
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