Answers Database
Virtex: Virtex has the potential race condition that can occur during the STARTUP
Record #8354
Problem Title:
Virtex: Virtex has the potential race condition that can occur during the STARTUP
Problem Description:
Urgency: Standard
Problem Description:
Virtex has the potential race condition that can occur during the STARTUP
sequence when sensing the state of DONE. The failure mode is that the global
tri-state net is not released keeping all IOs in the High-Z state. This has a higher
probability of appearing with a weak PULLUP on DONE and/or with a heavily
loaded DONE net.
Typically the designer will complain that all of pins are stuck high or if they are
using a CLKDLL that it's not working.
Solution 1:
There are two fixes for this:
1. On the board, use a 330ohm resistor to 3.3V for the DONE pin.
2. For the last Virtex device in the chain set the bitgen option
"-g DriveDone:Yes" This will actively drive the DONE pin high for
the last device.
End of Record #8354 - Last Modified: 01/03/00 13:14 |
