According to this (http://www.keil.com/c166/chips.asp) page, Keil supports the Infineon XC2000 family (which is compatible to the C166 architecture) in the 166 Developement Tools. Keil also supports the Segger J-Link, according to this (http://www.keil.com/support/man/docs/jlink/) page, but appearently only for Cortex-M based processors. When I create a XC2000 project, I can not chose the J-Link as my debug device.
Is it possible to start a jtag debug session on a XC2000 chip using a J-Link debugger?
"No, sadly I'm not sure"
Then you should clarify that point with Segger.
I guess it's possible that they used to, but don't any more? Or maybe the demand is just so small that they don't bother advertising it?
"As far as I know Keils ULink2 would work, right?"
Yes, that's my understanding - but clarify specifically with Keil and/or your distributor before parting with any cash...
Where are you getting your XC2000/C166 hardware from? Can they help you?
eg, http://www.keil.com/dd/chip/5448.htm lists 2 supported JTAG Debuggers ...
... here: http://www.keil.com/forum/62604/#/msg205416