Title: Indirect arithmetic control

Abstract: Circuits for the improved operation of microprogrammable computers are described. This improvement is accomplished by providing a set of read-only memory devices for storing the micro-code for all combinations of arithmetic logic unit function, carry bit and file register address than can be specified by an instruction word executed from Main Memory. In a universal microprogram designed to execute that family of Main Memory instructions that differ only in the functions specified above, the instruction word is used to address the read-only memory devices, the micro-code output of which is used to control the file, carry in bit and arithmetic logic unit. Through the use of these circuits a family of instructions may be executed by a single microprogram and at no increase in execution time over that required for the execution of a microprogram dedicated to a single instruction.

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Inventors: Mock, Howard C. (Rancho Palos Verdes, CA, US)
Isaac, Kenneth N. (Tustin, CA, US)
Disparte, Charles P. (Palos Verdes Peninsula, CA, US)
Hall, Warren L. (Palos Verdes Peninsula, CA, US)

Application Number: 425352
Filing Date: 1973-12-17
Publication_date: 1976-03-02
Assignee: Xerox Corporation (Stamford, CT)
Primary Class(es): 712/209 712/248
Other Classes:
US Patent Ref:

3117220	Jan, 1964	Wensley	340/172.
3416138	Dec, 1968	Brass	340/172.
3487369	Dec, 1969	King et al.	340/172.
3560933	Feb, 1971	Schwartz	340/172.

Other Refs:
Primary Examiner: Shaw, Gareth D.
Assistant Examiner: Sachs, Michael C.
Attorney: Ralabate; James J., Weiss; Franklyn C., Cunha; Robert E.