General Description: How do I connect the JTAG chain in a multi-processor Virtex-II Pro (2VP20)?
The PowerPC 405 Processor Block Reference Guide outlines the various methods for connecting the PowerPC 405 JTAG interface with the Virtex-II Pro Device JTAG logic.
When you connect the PPC405 JTAG logic in series with the dedicated Virtex-II Pro JTAG logic, only one JTAG chain is required on the printed circuit board. You can access all JTAG logic in the Virtex-II Pro through the dedicated JTAG pins on the Virtex-II Pro with this connection style.
For devices with more than one PPC405 core, you must connect the JTAG logic for ALL of the PPC405 cores on the device, even if some of the PPC405 cores are not used. Only the JTAG signals on unused PPC405 cores must be connected. The PPC405 core that first sees TDI from the JTAGPPC primitive recognizes the first four most significant bits in the Instruction Register; the next PPC405 core sees the next four most significant bits, and so on.
This solution provides an EDK example illustrating how to connect the two PowerPC 405 JTAG interfaces in series with the Virtex-II Pro Device JTAG logic.
For additional explanation, refer to the PowerPC 405 Processor Block Reference Guide: