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Virtex Configuration: Virtex devices do not pass anything out on DOUT pin during configuration
Record #7771
Problem Title:
Virtex Configuration: Virtex devices do not pass anything out on DOUT pin during
configuration
Problem Description:
Urgency: Standard
General Description:
Virtex devices do not pass data out on the DOUT pins during
configuraiton. How can I access this information?
Solution 1:
Virtex configuration data is completely different from previous Xilinx
families; it does not have the header, preamble, or length count
information at the beginning of the bitstream. Additionally, the
Virtex family does not "overflow" and pass configuration data out
of the DOUT register like previous FPGA families did.
Instead, the only way to pass data out through DOUT is by writing
to the LOUT register. LOUT is a Legacy Data Out register that
pipelines data to the DOUT pin.
Whenever a Virtex device is the only device in a configuration
chain, no data will be passed out of DOUT or written to the
LOUT register.
Whenever a Virtex device is in a configuration chain, it is
necessary to pass data out of DOUT to configure a complete
chain of devices. If the Prom File Formatter (or Promgen) is
used to contactenate bitstreams into a prom file, the required
writes to the LOUT register is taken care of automatically.
However, if a simple concatenation of the bit files is done, the
user must add the writes to the LOUT register, which will then
force the data to be passed through to the DOUT pin for chain
configuration.
For specific information on register writes, refer to Application Note
138: Virtex Configuration and Readback, available at (Xilinx XAPP138)
End of Record #7771 - Last Modified: 10/14/99 10:06 |
