Specify name of an FPGA load file to program the IO module. The filename is ice<iomname>_<sig> where: <iomname> is the IO module name - a2dr13, rfxd, flzrxdr1, etc. <sig> is the user defined signature, the first four characters being unique The 4 character signature embedded in the FPGA should be <sig[1:4]> If both modules are not the same, use IOM1FPGA=sig and IOM2FPGA=sig.