Nios® V/II Embedded Design Suite (EDS)
Support for Embedded Development Tools, Processors (SoCs and Nios® V/II processor), Embedded Development Suites (EDSs), Boot and Configuration, Operating Systems, C and C++
All support for Intel NUC 7 - 13 systems has transitioned to ASUS. Read latest update.
12583 Discussions

NiosV Ashling GDB "Debugger disconnected, closed connection to on port ..."

New Contributor I

I got this message when trying to Run or Debug a NiosV from Ashling Eclipse tools.


Ashling GDB Server for RISC-V (ash-riscv-gdb-server).

v22.3.2, 19-Aug-2022, (c)Ashling Microsystems Ltd 2022.


Initializing connection ...

Checking for an active debug connection using the selected debug probe (SN: 1):

Cannot set the JTAG frequency, continuing with auto adjust mode

Connected to target device "" using USB-Blaster-2 (1) via JTAG at 15.00MHz.

Info : Active Harts Detected : 1

Info : [0] System architecture : RV32

Info : [0] Number of hardware breakpoints available : 1

Info : [0] Number of program buffers: 8

Info : [0] Number of data registers: 2

Info : [0] Memory Access -> Program buffer

Info : [0] Memory Access -> Abstract access memory

Info : [0] CSR & FP Register Access -> Abstract commands


Waiting for debugger connection on port 50991 for core 0.

Press 'Q' to Quit.

Got a debugger connection from on port 50991.

[0x10000] Internal error. Abstract command execution failed: An abstract command is currently being executed.

Debugger disconnected, closed connection to on port 50991.

Quitting (Ctrl + C)...



It turned out to be that the FPGA clock source to the NiosV debug port was lower than the JTAG_CLOCK frequency.

(Same problems would apply to JTAG UART and other things connected via the SLD TAP(SystemLevelDebug TestAccessPort))



- Increase Clock source in your FPGA design

- Lower JTAG_CLOCK speed on the PC



0 Kudos
2 Replies

As we do not receive any response from you on the previous question/reply/answer that we have provided. Please login to ‘’, view details of the desire request, and post a feed/response within the next 15 days to allow me to continue to support you. After 15 days, this thread will be transitioned to community support. The community users will be able to help you on your follow-up questions.

0 Kudos