2077 - LatticeECP3: Can the default BSDL file provided on the Lattice website be used to test a programmed LatticeECP3 device after reinitialization?
Description:For LatticeECP3, the IO personality latches which is the I/O electrical properties such as Drive strength, buffer enable paths, open-drain, pullup/down/keeper is preserved after initial programming. These SRAM cells are not cleared by any other means but a power-on resetting clear or applying another bitstream to overwrite the latches. Therefore in cases where a device is programmed, any reinitialization by toggling PROGRAMN, REFRESH, or SRAM Erase commands will not completely clear the IO personality and will mismatch with the default BSDL file.
This LatticeECP3 feature is inherent to the device family to support TransFR(transparent field reconfigurable). This allows a design to hold its IO while the internal fabric is being changed. The default BSDL can be used after a programmed device is reinitialized only if the bit streams uses the INBUF=ON option. This is supported from the bitgen command line only. This will enable input paths on the unused input buffers and allow the default BSDL to work after initially programmed.