The MicroBlaze™ Debug Module supports multiple MicroBlaze™ cores, making it possible to use one MDM core for multiprocessor systems with up to 32 processors.
In general, when using internal BSCAN it is recommended to use a single MDM core for all processors. The reason for this is that each additional MDM core has to use a separate JTAG user-defined register. Because there are only four such registers available, with USER 1 usually reserved for hardware debug, it is a limited resource. Furthermore, the Xilinx® System Debugger (XSDB) command line only detects the MDM core connected to USER 2 by default, and needs to be configured to detect additional MDM cores. See the Vivado Design Suite User Guide: Programming and Debugging (UG908) for details.
When implementing a MicroBlaze™ multiprocessor design in Vivado using Block Automation, all processors are automatically connected to the same MDM core. See the Vivado Design Suite User Guide: Embedded Processor Hardware Design (UG898) for details.