188.8.131.52. Programming using External Flash Interface
This method allows parallel programming of the flash memory using the 16-bit data bus. An external processor or FPGA acts as the flash controller and has access to programming data using a communication link such as UART, Ethernet, and PCI. In addition to the program, erase, and verify operations, the external flash interface supports block or sector protection instructions.
External flash interface programming is only allowed when the configuration controller has relinquished flash access by tri-stating its internal interface. If the controller has not relinquished flash access during configuration or JTAG-based ISP, you must hold the controller in reset before initiating external programming. The controller can be reset by holding the FPGA nCONFIG line at a logic low level. This keeps the controller in reset by holding the nSTATUS-OE line low, allowing external flash access.