Hi everybody,
I have a custom pcb with a 20-pin standard Cortex-M debug connector. The schematic of the debug interface is equal to the one on page 26 in this document:
www.mouser.com/.../Board_Users_Manual_CPU_Board_XMC4500_General_Purpo-255431.pdf
The debuggers are ULINK2 and ULINKpro. When the ULINK is connected to the pcb, but not plugged into the PC it keeps the controller on the board in reset state. Only when the ULINK is powered the controller starts running. Why is that? Is it due to the schematic? What has to be done to prevent this behaviour?
Regards, Niclas
Does somebody else maybe also have this behaviour?
For anybody that might be interested: the signal-drivers in the Ulink2 are kept powered by the target VCC when the Ulink is disconnected from the PC. So the reset-line is pulled low by the Debugger. Inside the Ulink2 there is a jumper that has to be switched from the ARM-position to the 3,3v-position in order to prevent that the signal-drivers are powered when the debugger is disconnected from the PC. Unfortunately the ULINKpro doesn't have this jumper so it keeps resetting the target when it is not powered.
Greetings, Niclas