Only one device at a time can be debugged. If there is more than one device on the same JTAG scan chain, you must use the J-Link>JTAG Scan Chain options to specify which device to debug.
JTAG scan chain with multiple targets
Informs the debugger that there is more than one device on the JTAG scan chain.
Device position
Specify the position of the device you want to debug. The first device has position 0.
Use devices with deviant instruction register lengths
Informs the debugger that the JTAG instruction register of one or more devices on the JTAG scan chain has a non-standard length (the default length is 8 bits).
Preceding IR bits
Specify the combined length of the instruction registers of all devices that precede the device being debugged
