You can plug and unplug the JTAG cable without affecting the target. This is because the RVI debug unit includes power conditioning and switching circuitry.
You might want to do this if you have a target that is operating without a RVI run control 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 RVI run control unit and configure the connection without disturbing the state of the target. This requires that the RVI run control unit is powered before it is connected to the target.
When unplugging the JTAG connector, you must be aware of the following:
If you are using an RTCK system, make sure that no communication is taking place between the system and the RVI run control unit. Otherwise, if the RVI unit is waiting for a return clock, it might lock up. In this case, you must power down the RVI unit, and power it back up again.
If you are not using an RTCK system, the RVI software can handle this situation. However, you must arrange to do a TAP reset using the debugger when you next plug the RVI unit into a target.
See also- Tasks
- Concepts
- Reference
Using the Debug Hardware Configuration Utilities:
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