Usually locked in at an 8 MHz or 12 MHz crystal acting as the base clock for the chip's internal PLL.
The schematic uses specialized bidirectional level-shifting ICs, most notably the 74LVC8T245 or 74AVC4T245 . These chips have two separate power supply pins: VCCAcap V sub cap C cap C cap A end-sub (connected to the J-Link internal 3.3V) and VCCBcap V sub cap C cap C cap B end-sub (connected to the target's VTrefcap V sub cap T r e f end-sub jlink v9 schematic
: Most V9 designs utilize an STM32F205 series MCU. This chip provides the necessary USB 2.0 Full Speed connectivity and high-speed GPIOs for JTAG signaling. Usually locked in at an 8 MHz or
If your goal is education, copying the J-Link V9 schematic is a fascinating exercise in PCB routing (USB highspeed and SWD signals require impedance control). However, if you need a functional debugger, consider legal open-source alternatives that have superb schematics available: This chip provides the necessary USB 2