Adapter unit for use in a data processing system for processing a

Abstract

A data processing system includes a central processing unit, a main store and device controllers which couple to a bus system. Each controller has a number of device adapter units. One controller includes a real time adapter unit which instead of being connected to control a peripheral device is connected to provide a timer facility for use by the central processing unit (CPU) in executing tasks. The real time adapter unit includes a microprocessing section, a timer section, and a module time of day section. The time of day includes circuits which are connected to provide accurate and reliable time of day values. The timer module section includes circuits which are connected to provide variable time intervals. The circuits of both sections are connected to the circuits of the microprocessing section. In response to a number of different commands received from the central processing unit, the microprocessing unit (MPU) of the microprocessing section loads the various registers included within the timer module section to establish a desired interval at which it is to monitor the time of day operation of the time of day section. When the microprocessing unit establishes that the particular time of day operation specified by the central processing unit has been completed, it generates signals for notifying the central processing unit.