When using EDK's XMD to connect to a Spartan-3E device, the first 4 bits (revision value) of the IDCODE are all 0s, regardless of the actual device revision.
There is a problem in the XMD tool in EDK 8.2 and 9.1. XMD will always return a JTAG IDCODE revision value of "0," which means CES silicon. This might not be the actual revision of the silicon.
The XMD tool will be fixed in a future software revision.
To read the correct device revision code, use the iMPACT tool in ISE. In iMPACT, the revision bits in the IDCODE are read correctly.
Step 0 and Step 1 versions of the Spartan-3E silicon have different revision field values in the JTAG IDCODE. This change gives customers the opportunity to electrically identify Step 0 vs. Step 1, along with the marking differences. The Revision field is typically ignored by software tools such as iMPACT for device identification, but the user can read the IDCODE to determine the stepping level. The Revision field is the first four bits of the 32-bit value.