iMPACT batch mode gives an error when assigning the file to the BPI device for indirect BPI programming mode. When the following command is used:
assignfiletoattachedflash -position 2 -file "<filename>"
ERROR:iMPACT - No attached device found at position '1'.
This issue will be resolved in the ISE 10.1 release. The work around is to use the iMPACT GUI for Indirect BPI programming.