When programming the LatticeECP3 device using a Lattice programming cable, what is the purpose of "PROGRAMN/INITN/DONE" pins?
Lattice Programming cable support a number of Lattice FPGA devices, and in order to avoid multiple cables for multiple devices we have a single cable which supports all.
Sometimes PROGRAMN pin can be used to hold the device from being programmed or reinitialize the device by toggling PROGRAMN. Similarly, DONE pin can be used in certain cases where multiple devices are being programmed and you can tie all the DONE pins with external pull up to get an indication of system configuration. INITN pin is specifically required for the ORCA devices (ORCA 2,3,4).
This pins "PROGRAMN/INITN/DONE" of USB download cable are used for some old series devices. For LatticeECP3 devices, user may treat them as redundant ones.