POST_CRC will be stopped when iMPACT performs a Verify operation on a programmed Spartan-3A/-3AN/-3A DSP that has the POST_CRC feature enabled.
The reason that the POST_CRC function is stopped is because the iMPACT software Verify algorithm does not issue a DESYNC command. This command should be run at the conclusion of the operation to enable the POST_CRC feature.
This occurs in iMPACT version 14.x.
An optional work-around on Spartan-3A devices is to issue a Device Status Register read operation in iMPACT after the Verify operation to issue the DESYNC command.