2.3 About hot-plugging and unplugging the debug cable
There are times when you might want to connect or unplug a debug cable without powering off the target. You can do this provided certain conditions exist.
You can connect and disconnect the DSTREAM unit to the target hardware
without affecting operation of the target if:
- The DSTREAM unit is powered by its original, earthed-output power
- The target hardware is earthed either through its PSU or separate earth
You might want to connect the debug cable if you have a target that is
operating without a DSTREAM unit connected and you want to examine the target to find out
why it is behaving in a particular way. To do this, you must power-up the DSTREAM unit and
configure the connection without affecting the state of the target. This requires that the
DSTREAM unit is powered before it is connected to the target.
When unplugging the debug connector, you must be aware that:
- If you are using an RTCK system, make sure that no communication is
taking place between the system and the DSTREAM unit. Otherwise, if the DSTREAM unit is
waiting for a return clock, it might lock up.
- If you are not using an RTCK system, the debug software can handle this
situation. However, you must arrange to do a Test Access Port
(TAP) reset using the debugger when you next plug the DSTREAM unit into a target. This can
be performed during the advanced configuration part of the process.