The J-Link V9 is a USB-based debugger and programmer that supports a wide range of microcontrollers, including ARM-based devices, Cortex-M, and others. It is designed to work with various development environments, such as Keil, IAR Systems, and SEGGER's own Embedded Studio.
: LEDs for "Power" and "Activity" (usually connected to GPIO pins on the STM32).
Example pseudo-schematic connection:
If you work with ARM microcontrollers, the Segger J-Link is the industry standard. It’s the debug probe that every other probe is compared against. But while Segger is famous for their software—the J-Link SDK, RTT, and their blazing-fast download speeds—the hardware itself is often treated as a "black box."
If you are looking to develop features or repair a unit, these are the primary functional blocks: USB Connector:
The target microcontroller might run at 5V, 3.3V, or 1.8V. The J-Link V9 uses a combination of (like the 74LVC2T45 or TXB0108) to bi-directionally shift logic levels without distorting the SWD clock (SWCLK) and data (SWDIO) signals.