Forth specific language microprocessor

Abstract

A language specific microprocessor for the computer language known as FORTH is disclosed. The microprocessor includes four main registers each for holding a parameter; a L or instruction latch register for decoding instructions and activating microprocessor operation; an I or return index register for tracking returns; an N or next parameter register for operation with an arithmetic logic unit (ALU); and a T or top of parameter stack register with an appended ALU. A return stack port is connected to the I register and a parameter stack port is connected to the N register circuit, each have last in/first out (LIFO) memory stacks for reads and writes to isolated independent memory islands that are external to the microprocessor. The respective I, T and N registers are connected in respective series by paired bus connections for swapping parameters between adjacent registers. A first split 16 bit multiplexer J/K controls the LIFO stack for the I and N registers on paired 8 bit address stacks; a second 16 bit multiplexer designates the pointer to main memory with 65K addresses and an adjoining 65K for data. This addressing multiplexer receives selective input from a program counter P, the return index register I, the top of the parameter stack T and/or the instruction latch L. Movement to subroutine is handled in a single cycle with returns being handled at the end of any designated cycle. Asynchronous microprocessor operation is provided with the address multiplexer being simultaneously set up with an address to a future machine step, unloading from memory of appropriate data or instruction for the next machine step and asynchronously executing the current machine step. A two-phase clock latches data as valid on a rising edge and moves to a new memory location on a falling edge. This two phase clock is given a pulse width sufficient for all asynchronous cycles of microprocessor operations to settle. The microprocessor's assembler language is FORTH and the stack and main memory port architecture uniquely complements FORTH to produce a small (17,000 gates) fast (40 mips) microprocess or operable on extant FORTH programs. Provision is made for an additional G port which enables the current operating state of the microprocesor to be mapped, addressing of up to 21 bits as well as the ability to operate the microprocessor in tandem with similar microprocessors.