When reconfiguring a Spartan-3E device with iMPACT (i.e., a design is already loaded in the FPGA and a reconfiguration is done with a different bitstream without asserting PROG_B), the design does not work properly. In some cases, the device gets very warm after the reconfiguration is complete. Why is this occurring?
In 7.1.01i, iMPACT does not issue a JPROG instruction before configuring Spartan-3E. The JPROG instruction clears the configuration memory just like asserting PROG_B externally. Since the JPROG instruction is not issued, the configuration memory is not cleared before a new bitstream is loaded. This can cause contention in the configuration memory, which can cause the design to get hot and it can also cause the new design not to function properly as artifacts of the old design may remain.
To work around these issues, the PROG_B pin can be asserted externally every time a reconfiguration is performed or the "Pulse PROG" option on the iMPACT Program Options menu can be selected. The latter of the two options will force iMPACT to issue the JPROG command.
Starting with 7.1.02i, iMPACT will issue a JPROG instruction automatically when configuring Spartan-3E.
This problem has been fixed in the latest 7.1i Service Pack available at:
The first service pack containing the fix is 7.1i Service Pack 2.