1. Field of the Invention
The present invention relates to microprogrammed computers, wherein different operations are performed under control of a sequence of microinstructions forming a microprogram in firmware for managing the control system.
2. Description of Prior Art
On another patent application filed by the Applicant concurrently with the application of this invention, there was disclosed a device wherein each microprogram employed for managing the control system is stored either in a Read-Only Store (ROS), specifically dedicated to the microprograms, or in the Main Memory of the computer, thus making it possible to extend the set of microprograms of the computer without modifying the physical structure of the same. That patent application describes a preferred circuit embodiment which allows the use of microprograms stored in Main Memory, and clearly shows how execution of the microinstructions, or a sequence thereof, stored in the Main Memory, requires more time than the execution of microinstructions stored in the microprogram (ROS) memory. The reason for the increased execution time is that during the execution phase each microinstruction must always be preceded by a calling phase of the same microinstruction, which in turn requires at least one machine cycle.