Interface between a register file which arbitrates between a number of

Abstract

An interface protocol between a microprocessor register file (6) and a plurality of first functional units capable of independently executing first microinstructions that take a plurality of clock cycles to complete execution. A plurality of second functional units capable of independently executing second microinstructions that take a single clock cycle to complete execution. The first and second microinstructions are issued by an instruction decoder. A microintruction bus (112) is connected to the instruction decoder, the register file, and to each of the first and second functional units. A REG interface and a destination bus (110) are also connected to the register file (6). A Scbok line (102) is connected between the instruction unit, the register file and to each one of the first and second functional units. The instruction decoder includes means for asserting the Scbok line to signal that a current microinstruction on the microintruction bus (112) is valid. Means in the register file disassert the Scbok signal upon the condition that any one register in the register file needed by the instruction on the microinstruction bus is busy. An EU write line (102) connected from one of the single cycle functional units to the multiple cycle functional units is asserted by one of the single cycle functional units upon the condition that the single cycle functional unit requests access to the destination bus. The multiple cycle functional units and single cycle functional units are connected to the REG interface and to the destination bus. Arbitration means (3) in each of the multiple cycle functional units respond to the EU write line and to the Scbok line to prevent access to the destination bus upon the condition that the EU write line and the Scbo k line are asserted.