Jlink V9 Schematic ((exclusive)) -

: Resistors and capacitors are used to protect signal lines and filter noise. Some versions include high-current triodes (like the 8550) for reliable power delivery.

There is a long-standing debate in the community: Does the J-Link V9 use an FPGA?

One of the most appreciated features of the V9 is the . The firmware simply routes one of the MCU’s USART peripherals to the USB interface, creating a virtual COM port on the host PC. On the hardware side, the Tx and Rx pins of that USART (e.g., PA9, PA10) are connected to the level‑shifter and then to the debug connector.

The J-Link V9 schematic represents a design philosophy focused on rather than complex hardware logic. By utilizing a high-performance NXP LPC microcontroller and robust buffering, Segger created a hardware platform that acts as a transparent pipe between your PC and your target. jlink v9 schematic

Atmel AT91SAM3U4E (ARM Cortex-M3 core operating at up to 96 MHz).

With the VCOM feature, a single cable can provide both programming/debugging and a serial console connection – a huge convenience for development.

Let's take a closer look at some of the key components and sections of the J-Link V9 schematic: : Resistors and capacitors are used to protect

A standard 1117-3.3V LDO drops the incoming 5V USB VBUS down to a stable 3.3V for the internal microcontroller and logic chips.

Using such schematics to build a personal debugger for learning purposes is generally accepted as fair use. However, manufacturing and selling clones that use SEGGER’s proprietary firmware is a violation of the company’s license terms and may infringe on patents or trademarks.

Most open‑source J‑Link V9 schematics revolve around a single microcontroller: the . This 48‑pin Cortex‑M3 device was chosen for three specific reasons: One of the most appreciated features of the V9 is the

: Circuitry to detect the target board's voltage (VTref), allowing the probe to adjust its logic levels accordingly (1.2V to 3.3V). Interface Pinout (20-Pin JTAG)

| Pin | Signal | Pin | Signal | |-----|--------|-----|--------| | 1 | Vtref (Vref) | 2 | NC / 3.3V Out | | 3 | nTRST | 4 | GND | | 5 | TDI | 6 | GND | | 7 | TMS/SWDIO | 8 | GND | | 9 | TCK/SWCLK | 10 | GND | | 11 | RTCK (optional) | 12 | GND | | 13 | TDO/SWO | 14 | GND | | 15 | nSRST (reset) | 16 | GND | | 17 | UART RX (optional) | 18 | GND | | 19 | UART TX (optional) | 20 | GND |