General info & FAQs
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General info & FAQs
The number of IDEs supporting J-Link, as well as the high speed, ease-of use and support for flash breakpoints have made J-Link the de-facto standard for ARM emulators. Today J-Link is probably the most popular emulator for ARM cores. Unlike many of our competitors, we do not charge for software updates. All CPU families supported by the J-Link software can be used without additional license. |
FAQs
Advantages of J-Link versus other probes
| Q: | What is the advantage of J-Link versus simple probes such as FTDI based systems? |
| A: | J-Link has numerous advantages. One of the biggest advantages is the J-Link software supplied by SEGGER, which allows using it with common IDEs, the availability of flash breakpoints for people debugging software which runs in the flash of microcontrollers, as well as the high speed of the J-Link and the simple and very fast download into flash memory. In contrast to most of the simple probes, it supports adaptive clocking as well as SWD and SWO. It also works more stable since it is not just a dump USB to JTAG converter, but uses the intelligence of the built-in CPU, providing a more robust communication, especially in situations where the target CPU runs at low clock speeds. |
Using J-Link in my application
| Q: | I want to write my own application and use J-Link. Is this possible? |
| A: | Yes. We offer a dedicated Software Developer Kit (SDK). It allows using the full J-Link functionality. [More info...] |
J-Link Script files
| Q: | The core of my target system could not be recognized automatically. Is there a way to configure my device in order to communicate with J-Link? |
| A: | Yes! In most cases the J-Link auto-detection works fine and recognizes the core of a device automatically. However, in some cases the auto-detection of J-Link does not work e.g. if the core is not present in the JTAG chain by default and needs to be enabled by sending a command to another device in the JTAG-chain. In such cases, the connection sequence of J-Link can be customized by using a J-Link script file which is executed before the communication between J-Link and the target system starts. The script file allows maximum flexibility, so almost any target initialization which is necessary, can be supported. |
Multi-core debugging
| Q: | I have multiple ARM cores in my JTAG chain. How can I debug them (simultaneously) with J-Link? |
| A: | Simple: Two or more debuggers can use the same J-Link simultaneously. Multi-core debugging requires multiple debuggers or multiple instances of the same debugger. You need to tell your debugger which device in the scan chain you want to debug. Additional special settings are not required. |
Using multiple J-Links
| Q: | May I work with more than one J-Link at one time on the same machine? |
| A: | Yes, you can connect up to 4 J-Links to your PC. The only thing to do is, to give each J-Link a different USB address. By default, J-Link connects via USB-address 0. |
Supported CPUs
| Q: | Which CPUs are supported by J-Link? |
| A: | J-Link works with any ARM7/9/11, Cortex-M0/M1/M3/M4/R4 and Renesas RX600 series CPU. |
Maximum JTAG speed
| Q: | What is the maximum JTAG speed supported by J-Link? |
| A: | The maximum JTAG speed supported by J-Link is 12MHz. J-Link Ultra supports a maximum JTAG speed of 25MHz. |
Maximum download speed
| Q: | What is the maximum download speed into RAM? |
| A: | The maximum download speed is currently about 720 KByte/sec for J-Link and 1440 KByte/sec for J-Link Ultra when downloading into RAM. However, the actual speed depends on various factors, such as JTAG, clock speed, host CPU core etc. Take a look at the performance comparison to see how fast J-Link works in relation to other emulators. |
Read status of JTAG pins
| Q: | Can J-Link read back the status of the JTAG pins? |
| A: | Yes, the status of all pins can be read. This includes the outputs of J-Link as well as the supply voltage, which can be useful to detect hardware problems on the target system. |
J-Link support of ETB
| Q: | Does J-Link support the Embedded Trace Buffer (ETB)? |
| A: | Yes. J-Link supports ETB. Most current ARM7 / ARM9 chips do not have ETB built-in. |
J-Link support of ETM
| Q: | Does J-Link support the Embedded Trace Macrocell (ETM)? |
| A: | No. ETM requires another connection to the ARM chip and a CPU with built-in ETM. Most current ARM7 / ARM9 chips do not have ETM built-in. |
