Microcontroller with auxiliary register for duplicating storage of data

Abstract

A microcontroller is disclosed which executes all instructions in a fixed period machine cycle. A storage device is provided for storing data which is involved in the execution of instructions that are stored in a different memory device, such as a read only memory device. Specific locations in the data storage device are selected during execution of instructions by combining one partial storage address from two separate groups of partial storage address generators. One location '00' in the storage device is addressed automatically when no partial storage address generators are selected. An auxiliary register having a load control input terminal and the write input to the storage device are connected to a common source of data so that in response to certain instructions, the same data is entered into location '00' of the storage device and the auxiliary register from the data source during one fixed period machine cycle. A data path is also provided from the output of the auxiliary register to permit the auxiliary register to function as a partial storage address generator, and the path also extends through an ALU unit connected to the input of the data source to permit the original contents of the auxiliary register to be incremented during execution of certain other instructions.