J-Link GDB Server

The J-Link GDB Server is a remote server for the GDB. The GDB and GDB Server communicate via a TCP/IP connection, using the standard GDB remote serial protocol. The GDB Server translates the GDB monitor commands into J-Link commands.

GDB / GDB Server overview

The GNU Project Debugger (GDB) is a freely available debugger, distributed under the terms of the GPL. It connects to an emulator via a TCP/IP connection. It can connect to every emulator for which a GDB server software is available. The latest Unix version of the GDB is freely available from the GNU commitee under: http://www.gnu.org/software/gdb/download/

Licensing

J-Link GDB Server is distributed as "free for evaluation and non commercial use". The software can be used free of charge for educational and nonprofit purposes without an additional license. Without an additional license, download into RAM is limited to 32 KBytes. To download bigger programs or to use the software for other, especially commercial purposes, a license is required. With such a license, the download size is not limited.

Free evaluation licenses are available upon request. To obtain an trial or unlimited license, please contact sales@segger.com.

Full and valid license terms are specified in file License.txt which comes with the J-Link software and documentation package.

Note: When using J-Link GDB Server with ATMEL SAM-ICE or Digi JTAG Link, there is no limitation for download into RAM. Both J-Link OEM already have a built-in license for J-Link GDB Server.

Hardware requirements

To use the J-Link GDB Server, you have to meet the following hardware requirements:

PC running Win2K / XP
USB port
J-Link / J-Trace

User interface

The J-Link GDB Server's user interface shows information about the debugging process and the target connected via JTAG.

It shows:

host IP address, that is connected to the J-Link GDB Server
connection status of J-Link
information about the target core
measured target voltage
bytes that have been downloaded
status of target
log output of the J-Link GDB Server (optional, if log window is checked)
initial and current JTAG speed
target endianess

If a J-Link and target system is connected, the J-Link GDB Server should look similar to the following screen shot:

Setting up the J-Link GDB Server

Typically, most of the GDB setup is done from GDB via remote commands (monitor) in the ".gdbinit" file. However it is also possible to do the setup manually via user interface:

Via the JTAG speed drop down box the JTAG speed can be selected and with the box below the endianess of the target can be set. These two boxes will be grayed out while debugging, although their values can be changed from the debugger console using remote commands.

Log window

The log window is only visible if the checkbox Log window is selected. The log window shows all commands which the GDB sends to the GDB Server. The log window is primarily usefull for troubleshooting.

Log file

If log to file is checked, the GDB Server generates the log file C:\JLinkGDB.log.

Supported remote commands

J-Link GDB Server supports several remote commands from the GDB. This commands can be used from within a gdbinit file or the GDB console to initialize the target board and to setup J-Link GDB Server specific parameters.

Remote command	Explanation
ClrBP	Removes an instruction breakpoint.
Endian	Sets endianess of the target.
Go	Starts the target CPU.
Halt	Halts the target CPU.
JTAGConf	Configures a JTAG scan chain with multiple devices on it.
Long	Reads or writes from/to given address.
Reg	Reads or writes from/to given register.
Reset	Resets and halts the target CPU.
Select	Selects the way J-Link is connected to host system.
SetBP	Sets an instruction breakpoint at a given address.
Sleep	Sleeps for a given time period.
Speed	Sets the JTAG speed of J-Link / J-Trace.
Step	Performs one or more single instruction steps.
WaitHalt	Waits for target to halt code execution.
WIce	Writes to given IceBreaker register.