When reprogramming the embedded Flash on a secured LatticeXP2 device, the device will fail verification. This is due to the security fuse latch cannot be cleared by the conventional Erase command. The security fuse will prevent the device from being readback causing the verification to fail. The security fuse can be cleared but is not possible using conventional flash programming steps.
There are two solutions for reprogramming a secured LatticeXP2 device with Lattice ispVM programming software.
- Use Direct Programming mode with JTAG. Using this mode gives users the ability to disable the configuration mode by applying an ISC_DISABLE instruction followed by ISC_REFRESH which will wakeup the device and erase the security fuse. This permits the user to recover the device to an unsecure state with a new or a blank bitstream.
- If your system design requires Background Programming mode, use the XFLASH Erase, Program, Secure operation. This operation skips the post programming verification and allows the user to work past the verification step.