Using OpenOCD with AXS SDP

Synopsys DesignWare ARC Software Development Platforms (SDP) is a family of standalone platforms that enable software development, debugging and profiling. More information can be found at Synopsys web-site.

To debug applications on the AXS10x software development platforms you can use OpenOCD. Please consult with OpenOCD readme for instructions to download, build and install it.

AXS SDP consists of a mainboard and one of the CPU cards:

  • AXS101 uses AXC001 CPU card;
  • AXS102 uses AXC002 CPU card;
  • AXS103 uses AXC003 CPU card.


AXS103 with HS38x2 is not supported by OpenOCD - this system configuration includes SLC, which is not supported by OpenOCD. SLC cannot be disabled.


Binary toolchain releases can be downloaded from the GNU Toolchain Releases page. For Linux hosts there is a choice between complete tarballs that include toolchain, IDE and OpenOCD, and tarballs that include toolchain only. For Windows hosts there is only a single installer, that contains all of the Toolchain components and allows to select which ones to install.


In order to use OpenOCD it is required to install appropriate WinUSB drivers, see How to Use OpenOCD on Windows for details.

Building an application

To learn how to build and debug application with Eclipse IDE, please use ARC GNU IDE manual.

A memory map appropriate to the selected board should be used to link applications. This “toolchain” repository includes memory maps for all ARC SDP systems. They can be found in the tree. Memory map files in that directory have .x extension and file to be used should be renamed to memory.x, because arcv2elfx linker emulation doesn’t support ability to override that file name. Please refer to linker page Linker scripts and memory.x files for more details about memory.x files.

For example to build an application for AXS103/HS36:

$ cp -a toolchain/extras/dev_systems/axs103.x memory.x
$ arc-elf32-gcc -Wl,-marcv2elfx --specs=nosys.specs -O2 -g \
    -mcpu=hs38_linux test.c -o test.elf
List of compiler flags corresponding to particular CPUs
101 EM6 -mcpu=em4_dmips -mmpy-option=3
ARC770 -mcpu=arc700
AS221 -mcpu=arc600_mul32x16
102 HS34 -mcpu=hs -mdiv-rem -mmpy-option=9 -mll64 -mfpu=fpud_all
HS36 -mcpu=hs -mdiv-rem -mmpy-option=9 -mll64 -mfpu=fpud_all
103 HS36 -mcpu=hs38_linux
HS38 -mcpu=hs38_linux

Board configuration

First it is required to set jumpers and switches on the mainboard:

  • PROG_M0 (JP1508), PROG_M1 (JP1401) and BS_EN (JP1507) jumpers should be removed (it is their default position);
  • PROG_SRC (JP1403) jumper should be removed (default); DEBUG_SRC (JP1402) jumper should be placed (default); SW2501, SW2502, SW2503 and SW2401 should be set to their default positions according to the AXC00x CPU Card User Guides depending on what CPU card is being used. Following changes should be applied then:
    • SW2401.10 switch should be set to “1” (moved to the left), this will configure bootloader to setup clocks, memory maps and initialize DDR SDRAM and then halt a CPU.
    • For the core you are going to debug choose “Boot mode” type “Autonomously”, this is done by moving top two switches of the respective switch block to the position “1”. Alternatively, if you leave default boot mode “By CPU Start Button” you need to press “Start” button for this CPU, before trying to connect to it with the OpenOCD.

Configuration of the JTAG chain on the CPU card must match the configuration in the OpenOCD. By default OpenOCD is configured to expect complete JTAG chain that includes all of the CPU cores available on the card.

  • For the AXC001 card jumpers TSEL0 and TSEL1 should be set.
  • For the AXC002 card jumpers JP1200 and JP1201 should be set.
  • For the AXC003 card it is not possible to modify JTAG chain directly.

Reset board configuration after changing jumpers or switch position, for this press “Board RST” button SW2410 near the power switch. Two seven-segment displays should show a number respective to the core that is selected to start autonomously. Dot should appear on the first display as well, to notify that bootloader was executed in bypass mode. To sum it up, for the AXS101 following numbers should appear:

  • 1.0 for the AS221 core 1
  • 2.0 for the AS221 core 2
  • 3.0 for the EM6
  • 4.0 for the ARC 770D.

For the AXS102 following numbers should appear:

  • 1.0 for the HS34
  • 2.0 for the HS36.

For the AXS103 following numbers should appear:

  • 1.0 for the HS36
  • 2.0 for the HS34
  • 3.0 for the HS38 (core 0)
  • 4.0 for the HS38 (core 1)

Running OpenOCD

Run OpenOCD for the AXS101 platform:

$ openocd -f board/snps_axs101.cfg

Or run OpenOCD for the AXS102 platform:

$ openocd -f board/snps_axs102.cfg

AXS103 SDP supports different core configurations, so while in AXS101 and AXS102 there is a chain of several cores, which can operate independently, in AXS103 one of the particular configurations is chosen at startup and it is not possible to modify chain via jumpers. As a result, different OpenOCD configuration files should be used depending on whether AXS103 is configured to implement HS36 or to implement HS38.

To run OpenOCD for the AXS103 platform with HS36:

$ openocd -f board/snps_axs103_hs36.cfg

To run OpenOCD for the AXS103 platform with HS38x2:

$ openocd -f board/snps_axs103_hs38.cfg

Note, however, that as of version 2016.03 OpenOCD doesn’t support SLC in HS38x2, rendering it mostly useless for HS38x2 debugging.

OpenOCD will open a GDBserver connection for each CPU core on target (4 for AXS101, 2 for AXS102, 1 or 2 for AXS103). GDBserver for the first core listens on the TCP port 3333, second on port 3334 and so on. Note that OpenOCD discovers cores in the reverse order to core position in the JTAG chain. Therefore for AXS101 port assignment is following:

  • 3333 - ARC 770D
  • 3334 - ARC EM
  • 3335 - AS221 core 2
  • 3336 - AS221 core 1.

For AXS102 ports are:

  • 3333 - ARC HS36
  • 3334 - ARC HS34.

For AXS103 HS38x2 ports are:

  • 3333 - ARC HS38 core 1
  • 3334 - ARC HS38 core 0.

Running GDB

Run GDB:

$ arc-elf32-gdb ./

Connect to the target GDB server:

(gdb) target remote <gdbserver-host>:<port-number>

where <gdbserver-host> is a hostname/IP-address of the host that runs OpenOCD (can be omitted if it is a localhost), and <port-number> is a number of port of the core you want to debug (see previous section).

In most cases it is needed to load application into the target:

(gdb) load

After that application is ready for debugging.

To debug several cores on the AXC00x card simultaneously, it is needed to start additional GDBs and connect to the required TCP ports. Cores are controlled independently from each other.

Advanced topics

Using standalone Digilent HS debug cable

It is possible to use standalone Digilent HS1 or HS2 debug cable instead of the FT2232 chip embedded into the AXS10x mainboard. Follow AXS10x mainboard manual to learn how to connect Digilent cable to mainboard. In the nutshell:

  • Connect cable to the DEBUG1 6-pin connector right under the CPU card. TMS pin is on the left (closer to the JP1501 and JP1502 jumpers), VDD pin is on the right, closer to the HDMI connector.
  • Disconnect JP1402 jumper.

Then modify board configuration file used (board/snps_axs101.cfg, board/snps_axs102.cfg, etc): replace “source” of snps_sdp.cfg with “source” of digilent-hs1.cfg or digilent-hs2.cfg file, depending on what is being used.

Then restart OpenOCD.

Using OpenOCD with only one core in the JTAG chain

In AXS101 and AXS102 it is possible to reduce JTAG chain on the CPU card to a single core.

Change positions of TSEL0/TSEL1 (on AXC001) or JP1200/JP1201 (on AXC002) to reduce JTAG chain to a particular core. Follow AXC00x CPU Card User Guide for details.

Then modify OpenOCD command line to notify it that some core is not in the JTAG chain, for example:

$ openocd -c 'set HAS_HS34 0' -f board/snps_axs102.cfg

In this case OpenOCD is notified that HS34 is not in the JTAG chain of the AXC002 card. Important notes:

  • Option -c 'set HAS_XXX 0' must precede option -f, because they are executed in the order they appear.
  • By default all such variables are set 1, so it is required to disable each core one-by-one. For example, for AXS101 it is required to set two variables. * Alternative solution is to modify target/snps_axc001.cfg or target/snps_axc002.cfg files to suit exact configuration, in this case there will be no need to set variables each time, when starting OpenOCD.

Those variables are used in the target/snps_axc001.cfg file: HAS_EM6, HAS_770 and HAS_AS221 (it is not possible to configure AXC001 to contain only single ARC 600 core in the JTAG chain). Those variables are used in the target/snps_axc002.cfg file: HAS_HS34 and HAS_HS36.

When JTAG chain is modified, TCP port number for OpenOCD is modified accordingly. If only one core is in the chain, than it is assigned 3333 TCP port number. In case of AS221 TCP port 3333 is assigned to core 2, while port 3334 is assigned to core 1.


  • OpenOCD prints “JTAG scan chain interrogation failed: all ones”, then there is a lot of messages “Warn : target is still running!”.

    An invalid JTAG adapter configuration is used: SDP USB data-port is used with configuration for standalone Digilent-HS cable, or vice versa. To resolve problem fix file board/snps_axs10{1,2}.cfg or board/snps_axs103_hs36.cfg depending on what board is being used.

  • OpenOCD prints “JTAG scan chain interrogation failed: all zeros”.

    It is likely that position of JP1402 jumper does not match the debug interface you are trying to use. Remove jumper if you are using external debug cable, or place jumper if you are using embedded FT2232 chip.

  • OpenOCD prints that is has found “UNEXPECTED” device in the JTAG chain.

    This means that OpenOCD configuration of JTAG chain does not match settings of jumpers on your CPU card.

  • I am loading application into target memory, however memory is still all zeros.

    This might happen if you are using AXC001 CPU card and bootloader has not been executed. Either run bootloader for the selected core or configure core to start in autonomous mode and reset board after that - so bootloader will execute.

  • OpenOCD prints “target is still running!” after a CTRL+C has been done on the GDB client side.

    There is an issue with EM6 core in AXS101 - after OpenOCD writes DEBUG.FH bit to do a force halt of the core, JTAG TAP of this core still occasionally returns a status that core is running, even though it has been halted. To avoid problem do not try to break execution with Ctrl+C when using EM6 on AXS101.