This instruction fills one entry of the Multiply unit's LookUp Table (LUT). It is used at boot-time in the versions of the YASEP architecture that use a SRAM-assisted multiplier (like with Actel's FPGA).
It is a necessary to initialise the whole LUT before MUL8L and MUL8H can work correctly, and MULI is an implementation-specific opcode used during system powerup. This opcode is used for early versions of YASEP16 and may evolve in later versions. This instruction writes to the LUT and no result goes to the register set, so it can not be aborted.
The order of the operands and the purpose of each field is similar to that of the MUL8x instructions, with the added field of the initialisation value.