For Virtex and Virtex-E devices, what should the output levels of the TDO pin be?
For Virtex and Virtex-E devices, the JTAG TDO pin is powered by the VCCO in bank 2. The TDO pin will always switch rail-rail between Ground and the voltage level that appears on this pin. For Virtex/-E devices, any voltage level can be placed on VCCO, provided that the level is within the recommended operating conditions specified in the data sheet.
- Noise margin and the input switching levels on the downstream device TDI pin
- Any voltage requirements that other user outputs in bank 2 might have
For most applications, VCCO should be set to 3.3V.
Related Answer Records:
- For information on the switching levels of JTAG input pins, see (Xilinx Answer 7738).
- For information on I/O switching levels during Boundary Scan testing (EXTEST), see (Xilinx Answer 8762).
- For information on IBIS simulations for JTAG pins, see (Xilinx Answer 12085).