Patent US 4,351,024

Firmware is provided to change, upon execution, information in the system base which is located in both main memory and internal scratch pad registers. Hardware structures controlled by a microprogrammed control store, which provides for the generation of signals causing the creation of an image in main memory of a communication center comprised of registers at another location in the central processing unit. The microprogrammed control store further generates signals which causes the interchange of the information between the communication center and its image.