AR# 64764

Vivado Logic Analyzer - Warning: [Labtools 27-3123] The debug hub core was not detected at User Scan Chain 1 or 3


When programming the device in Hardware Manager for a design with ILA, I receive the following warnings:

WARNING: [Labtools 27-3123] The debug hub core was not detected at User Scan Chain 1 or 3.
1. Make sure the clock connected to the debug hub (dbg_hub) core is a free running and is active OR
2. Manually launch hw_server with -e "set xsdb-user-bscan <C_USER_SCAN scan_chain_number>" to detect the debug hub at User Scan Chain of 2 or 4.
WARNING: [Labtools 27-1974] Mismatch between the design programmed into the device <device_name> and the probes file <file_name.ltx>.

How can I resolve this issue?


The clock net connected to dbg_hub is automatically selected by the tool based on the debug core configuration and connections.

However, you can change this clock net by modifying the "connect_debug_port" command in XDC.

The following are possible causes and solutions:

1. The clock that is connected to dbg_hub is a non-free-running clock.

  • To check which clock net is connected to the dbg_hub, follow these steps in the Vivado GUI:
    Open the Synthesized design or Implemented design -> Right click the dbg_hub core in the netlist hierarchy and select "Schematic" -> Double click the "clk" pin
  • If this clock is a non-free-running clock, change it to a free running one by modifying this command in XDC:

    connect_debug_port dbg_hub/clk [get_nets <clock_net_name>]

2. The clock is a free running clock but the signal integrity of this clock net is not good.

Check if the quality of this clock signal on the board is good or not. One example of this issue is if the daughter card connector is not inserted tightly (clock is coming from the daughter card).

3. Try the second solution mentioned in the warning message which is to use the other User Scan Chain number. 

For example, the following are the steps to change to use Scan Chain number 2:

  • Change the C_USER_SCAN_CHAIN property of the dbg_hub core to 2. Please refer to (UG908) for how to change this property.
  • Manually launch hw_server in the Windows command prompt or a terminal on Linux:

    hw_server -e "set xsdb-user-bscan <C_USER_SCAN_CHAIN 2>
AR# 64764
Date 10/28/2015
Status Active
Type General Article