A 22-bit floating point registered arithmetic logic unit

The LSI Products Division of TRW is currently developing a third chip for its growing family of 22-bit floating point arithmetic devices. Joining the adder and the multiplier later this year will be the registered arithmetic logic unit (RALU), built in TRW\´s dual-metal one-micron bipolar "Omicron-B" process. Operating at a guaranteed (military temperature and supply voltage ranges) speed of 6 MHz, this device will be able to store, retrieve, add, subtract, and normalize 22-bit floating point numbers, convert between 22-bit floating point and 16-bit fixed point formats, and add, subtract, and perform logical operations on 16-bit fixed point numbers. With its built-in shifters and controls, it can also perform a fixed point multiplication or division or a floating point division in 16 clock cycles. The architecture of the RALU is very similar to that of the widely used 2901 four-bit microprocessor slice. The bus widths have been widened from 4 to 22 bits and the instruction set has been expanded to encompass the eight standard 2901 functions (for fixed point) and eight additional floating point and fixed-float conversion operations. The 2901\´s internal dual port RAM has been retained and widened for a 22-bit word size.