Hi at all, I designed a my own Cirrus ARM 9307 board. Now I started with commissioning. I started J-Link Commander (V3.78d). The message is : "Info: TotalIRLen=4, IRPrint = 0x01" "JTAG Speed: 29kHz" "Info: Using DBGRQ to halt CPU" "Resetting TRST in order to halt CPU" "Info: CP15.0.0, 0x41129200, ARM, architecture 4T" "Error: unable to halt ARM core" "Trying to connect with 5kHz!" It's also not possible to debug a blinky in IAR IDE. HW-Info