142 - What is a possible reason for the INITn pin going low while loading configuration image from SPI flash device?

142 - What is a possible reason for the INITn pin going low while loading configuration image from SPI flash device?

One possible reason for a configuration loading error can be the image content loaded into the SPI flash. Some serial SPI Flash devices do not guarantee the data integrity of the first few bytes during a read. To address the issue, the LatticeECP2/2M/3 devices are designed to ignore the first 128 bits of data from the SPI Flash devices. Therefore, the first 128 bits (or 16 bytes) in the bitstream file must be dummy (0xFF). The presence of the bit stream header (~300 bytes) serves as the required dummy cycles. Having an image that is missing these dummy bits can cause the configuration logic to error causing INITn to signal the error condition.

Some work arounds include:

  1. Do not set the No Header option to True in Lattice ispLEVER or Diamond Design Tools when generating the bitstream if the bitstream will be programmed into a SPI Flash device.
  2. Do not use rawbit formatted bitstreams with Lattice ispVM to write configuration image to flash. This software option does not maintain the adequate padding.
  3. Lattice Universal File Writer can be used to insert the dummy data into the bitstream with no header.