In iMPACT 12.x if you try to generate a SVF/XSVF file that verifies the internal flash of Spartan-3AN FPGA, you get a error:
1': Verifying device...ERROR:iMPACT - writeLength is not equal to readLength.
If you play this SVF on 3AN ISF, the following error occrus:
ERROR:iMPACT - On line 69055,Failed ScanDR: TDO .......
does not match Expected TDO .......
EXCEPTION:iMPACT:SVFReader.c:376:1.30 - Scan Data Mismatch.
INFO:iMPACT:2146 - Play svf failed.