J-Link Probes

J-Link debug probes are the most popular choice for optimizing the debugging and flash programming experience. Benefit from record-breaking flash loaders, up to 4 MB/s RAM download speed and the ability to set an unlimited number of breakpoints in the flash memory of MCUs.

J-Link also supports a wide range of CPUs and architectures. Everything from single 8051 to mass market Cortex-M to high-end cores like Cortex-A (32- & 64-bit).

J-Link supports directly interfacing SPI flashes, without the need of a CPU between J-Link and the SPI flash (directly communicating via the SPI protocol). J-Link is further supported by all major IDEs, from free Eclipse-based ones (directly or via GDB) up to commercial ones, including SEGGER Embedded Studio.

Key features

  • Ultra-fast download speed
  • Unlimited breakpoints in flash memory (Flash Breakpoints)
  • Real-Time Transfer technology for extended debug information
  • Built-in virtual COM port functionality (VCOM)
  • All popular devices are supported (Arm, RISC-V, Microchip, Renesas, SiLabs 8051, Cadence)
  • All popular debuggers are supported
  • Includes software and firmware updates
  • Includes use on all target devices currently supported, and on any that will be added

J-Link SDK

The J-Link Software Developer Kit (SDK) allows customers to integrate J-Link support into their own applications. This is used in professional IDEs like IAR EWARM or KEIL uVision to allow debugging directly via a J-Link, as well as in customized production utilities.

J-Link DSK

The J-Link Device Support Kit (DSK) enables silicon vendors and customers to add support for new devices on their own. While SEGGER maintains the updating of J-Link software with new devices, some devices might be left out in the process. To enable customers to fill in the gaps on their own, the J-Link DSK is offered.

Ultra-fast download speed

J-Link makes Flash memory feel almost like RAM. Since it comes with a set of speed-optimized, built-in flash loaders it can easily and quickly be downloaded into flash memory.

J-Link Download Speed

Built-in virtual COM port

J-Link PRO, J-Link ULTRA+, J-Link WiFi, J-Link PLUS and J-Link BASE each comes with built-in virtual COM port (VCOM) functionality. This means that in addition to the regular J-Link debug functionality, J-Link will also show up as a COM port in the device manager of the operating system.

Most modern computers don’t have a physical COM port anymore. However, many hardware setups still use UARTs for logging, diagnostics and application control. That’s why a separate COM to USB adapter is needed to get full COM functionality of the target hardware, while debugging at the same time. With J-Link, there’s no need for an additional adapter since J-Link already provides this adaption functionality.

The J-Link VCOM functionality is implemented via SEGGER emUSB-Device, using the CDC-ACM class. J-Link models are shipped with VCOM functionality disabled. It can be enabled via the J-Link Configurator utility.

Please note:

  • VCOM functionality is not available for the J-Link EDU Mini model.
  • VCOM functionality is not available when using the traditional 4-wire JTAG interface for target communication, as Pin 5 is needed as TDI for this interface.



The universal debug probe

The J-Link PRO is SEGGER’s versatile JTAG/SWD programming and debug probe with USB and Ethernet interfaces.

J-Link Ultra Plus

The ultra-fast debug probe

The J-Link ULTRA+ is an ultra-fast debug probe for JTAG/SWD. It is 100% compatible with J-Link PLUS, just faster.

J-Link WiFi

The debug probe with WLAN/WiFi interface

The J-Link WiFi is a JTAG/SWD debug probe with WLAN/WiFi interface. It can communicate at high speed (up to 15 MHz) with the supported target CPUs.

J-Link Plus

The JTAG/SWD debug probe with USB interface

Based on a 32-bit RISC CPU, the J-Link PLUS can communicate at high speed with the supported target CPUs.

J-Link PLUS is available in two form factors with identical function: J-Link PLUS Classic and J-Link PLUS Compact.

J-Link Base

The JTAG/SWD debug probe with USB interface

Based on a 32-bit RISC CPU, the J-Link BASE is the base version of the market-leading debug probe family.

J-Link BASE is available in two form factors with identical function: J-Link BASE Classic and J-Link BASE Compact.

J-Link EDU Mini

The small-size educational debug probe

The J-Link EDU Mini in a reduced form factor has been designed for educational purposes. It allows students and educational facilities as well as hobbyists access to top of the line debug probe technology.

J-Link OB

The on-board debug probe

The J-Link OB is an on-board debug probe that turns an evaluation board into a complete evaluation kit. It is a cost-effective way to allow customers to fully use, test, and debug the target device right out of the box.

J Link Pro Poe

The specialized high-end debug probe for test farms

J-Link PRO PoE is SEGGER’s specialized programming and debug probe for creating test farms. It can draw power via Ethernet and supplies power to the target either via debug interface or a USB A connector.



Ozone is the debugger for J-Link and J-Trace. It includes all well-known debug controls and information windows and makes use of the best performance of J-Link and J-Trace debug probes.



SystemView is a real-time recording and visualization tool for embedded systems, revealing the true runtime behavior of an application. In fact, it even goes far deeper than system insights provided by standard debuggers.

Embedded Studio

Embedded Studio

Embedded Studio is a complete, all-in-one solution for managing, building, testing, and deploying embedded applications. It is the best solution for embedded C programming: with a Visual Studio-like appearance, embedded engineers get the same intuitive usage PC developers enjoy.


Wide IDE support

J-Link supports SEGGER’s own software, of course, while also offering support for a host of 3rd-party embedded system development options.

GDB support

J-Link can be used with GDB-based setups. The GNU Debugger (GBD) is the de facto debugger for development on Linux systems. However, it has now found its way into embedded development (even without Linux running on the target system). GDB provides a standardized interface / API that can be used by an IDE.

It also specifies a standardized protocol (GDB remote protocol) which allows GDB to communicate with a GDBServer which knows how to handle the debug probe connected to the target. The J-Link Software and Documentation Package comes with the J-Link GDB Server which allows using J-Link in GDB-based setups.

LLDB support

J-Link can be used with LLDB. Originally, GNU toolchains provided GCC as a compiler and GDB as a debugger. Since Clang’s introduction as a compiler, LLDB was introduced (which was essentially a GDB successor). In terms of protocol, it is backward compatible to GDB whilst the API for the IDE is slightly different.

The J-Link Software and Documentation Package comes with the J-Link GDBServer. This permits the use of J-Link in LLDB-based setups.

OpenOCD support

J-Link can be used with OpenOCD (Open On-Chip Debugger). OpenOCD is an open-source software that can interface basically any debug probe. It provides a standardized API, allowing an IDE to support OpenOCD. There are several tutorials on the internet that describe how to use J-Link with OpenOCD.

Please note: OpenOCD is a 3rd party software, so SEGGER cannot provide any guarantees, etc. Using J-Link with OpenOCD bypasses all J-Link specific features like flash programming, unlimited flash breakpoints and the J-Link high debugging speed. OpenOCD will handle J-Link as a simple sequence generator which will affect debug performance. Please also note that using J-Link with OpenOCD is not covered by the standard J-Link support. Support for OpenOCD is provided by the OpenOCD community.


The table below shows features of each J-Link debug probe in comparison.

J-Link PROJ-Link ULTRA+J-Link WiFiJ-Link PLUSJ-Link BASEJ-Link EDU Mini
Hardware specifications [1]
Download speed into RAM [2]4.0 MB/s4.0 MB/s1.0 MB/s1.0 MB/s1.0 MB/s200 KB/s
Max. target interface speed50 MHz50 MHz15 MHz15 MHz15 MHz4 MHz
Max. SPI interface speed50 MHz50 MHz12 MHz12 MHz12 MHz4 MHz
Max. SWO speed100 MHz100 MHz30 MHz30 MHz30 MHz100 MHz
Max. VCOM speed10 MBd10 MBd115200 Bd115200 Bd115200 Bd
High Speed Sampling BandwidthUnlimited [3]Unlimited [3]1 kHz [4]1 kHz [4]1 kHz [4]1 kHz [4]
Supported target voltage1.2 V – 5 V1.2 V – 5 V1.2 V – 5 V1.2 V – 5 V1.2 V – 5 V3.3 V
Host interfaces
EthernetSupportedNot SupportedNot SupportedNot SupportedNot SupportedNot Supported
WiFiNot SupportedNot SupportedSupportedNot SupportedNot SupportedNot Supported
Target interfaces
cJTAG SupportedSupportedSupportedSupportedSupportedSupported
JTAG SupportedSupportedSupportedSupportedSupportedSupported
SWD SupportedSupportedSupportedSupportedSupportedSupported
SWO SupportedSupportedSupportedSupportedSupportedSupported
Microchip ICSPSupportedSupportedSupportedSupportedSupportedNot Supported
Renesas FINESupportedSupportedSupportedSupportedSupportedNot Supported
VCOMSupportedSupportedSupportedSupportedSupportedNot Supported
Trace interfaces [5]
ETB/MTB TraceSupportedSupportedSupportedSupportedSupportedSupported
Cortex ETM TraceNot SupportedNot SupportedNot SupportedNot SupportedNot SupportedNot Supported
Cortex-A PTM TraceNot SupportedNot SupportedNot SupportedNot SupportedNot SupportedNot Supported
SiFive Nexus Trace BTMNot SupportedNot SupportedNot SupportedNot SupportedNot SupportedNot Supported
Software features
Flash Download SupportedSupportedSupportedSupportedSupportedSupported
GDB Server SupportedSupportedSupportedSupportedSupportedSupported
J-Flash SupportedSupportedSupportedSupportedNot SupportedNot Supported
Ozone SupportedSupportedSupportedSupportedNot SupportedSupported
RDDISupportedSupportedSupportedSupportedNot SupportedNot Supported
RDI SupportedSupportedSupportedSupportedNot SupportedNot Supported
Real-Time Transfer (RTT) SupportedSupportedSupportedSupportedSupportedSupported
Unlimited Flash Breakpoints SupportedSupportedSupportedSupportedNot SupportedSupported
Arm CoreSight SoC-400 and earlierSupportedSupportedSupportedSupportedSupportedSupported
Arm CoreSight SoC-600SupportedSupportedSupportedSupportedSupportedSupported

Supported Arm cores

Cortex-A53SupportedSupportedSupportedSupportedSupportedNot Supported
Cortex-A72SupportedSupportedSupportedSupportedSupportedNot Supported
SC000 (M0 secure)SupportedSupportedSupportedSupportedSupportedSupported
SC300 (M3 secure)SupportedSupportedSupportedSupportedSupportedSupported
Supported Arm legacy cores
Arm7SupportedSupportedSupportedSupportedSupportedNot Supported
Arm9SupportedSupportedSupportedSupportedSupportedNot Supported
Arm11SupportedSupportedSupportedSupportedSupportedNot Supported
Supported Cadence cores
HiFi 1SupportedSupportedSupportedSupportedSupportedNot Supported
HiFi 3SupportedSupportedSupportedSupportedSupportedNot Supported
HiFi 3zSupportedSupportedSupportedSupportedSupportedNot Supported
HiFi 4SupportedSupportedSupportedSupportedSupportedNot Supported
Fusion F1SupportedSupportedSupportedSupportedSupportedNot Supported
Xtensa LX6SupportedSupportedSupportedSupportedSupportedNot Supported
Xtensa LX7SupportedSupportedSupportedSupportedSupportedNot Supported
Supported Microchip PIC32 cores
Microchip PIC32MXSupportedSupportedSupportedSupportedSupportedNot Supported
Microchip PIC32MZSupportedSupportedSupportedSupportedSupportedNot Supported

Supported Renesas RX cores

Renesas RX110SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX111SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX140SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX210SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX21ASupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX220SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX610SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX621SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX62GSupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX62NSupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX62TSupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX630SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX631SupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX63NSupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX63TSupportedSupportedSupportedSupportedSupportedNot Supported
Renesas RX660SupportedSupportedSupportedSupportedSupportedNot Supported
Supported RISC-V cores
Supported SiLabs 8051 cores
EFM8SupportedSupportedSupportedSupportedNot SupportedSupported

[1] The hardware features overview always refers to the current hardware version of the appropriate model. Older hardware versions may not support all of the features mentioned here.

[2] The download speeds listed here are the peak download speeds that can be achieved by the particular J-Link model. The actual download speed may be lower as it depends on various factors, such as, but not limited to: The selected debug interface and speed, the CPU core and its operating frequency, other devices in the JTAG chain in case JTAG is used as target interface.

[3] Only limited by the bandwidth of the debug interface. Typical sampling frequency of one variable: > 10 kHz.

[4] Max. sampling frequency is guaranteed for sampling one variable and for appropriate target interface speeds being selected (min. 1 MHz). Sampling more than one variable in parallel, may lead to a smaller max. sampling frequency. When this threshold of sampling frequency decrease is hit, depends on different factors (number of variables to be sampled in parallel, size of each variable, selected target interface speed, etc.).

[5] For full trace support, please refer to SEGGER’s J-Trace streaming trace probes.