Abstract: In a data processing system having a system controller unit (SCU) which interfaces a plurality of equipments with a memory unit, the SCU determines which of the equipments will be permitted to communicate with the SCU or memory unit in response to a request from the equipments. The SCU includes an activity monitor and control apparatus which determines whether the request from the equipments can be accepted. The activity monitor and control apparatus comprises a plurality of first elements, each of the first elements being assigned to monitor a request which has been accepted. The activity monitor and control apparatus monitors the operations with the SCU thereby providing status information of the SCU. A plurality of second elements, which is operatively connected to the first elements, combines preselected status information to generate control signals thereby indicating current and future availability of the SCU in order to determine whether a request can be accepted.

Abstract: Lock-out of pending higher high priority requests to a system controller is prevented by a circuit which comprises a counter element for counting the number of times the pending higher high priority request is not granted access. The counting results in a count value which is temporarily stored in the counter element. A compare element compares the count value to a predetermined value, the predetermined value being a predetermined number of times the data processing system will permit bypassing the pending higher high priority request. A control signal is outputted from the compare element when the count value is equal to the predetermined value and is coupled to each port to inhibit any further request for access from the equipment from being accepted by the system controller.

Abstract: The apparatus controls access to at least one subsystem in response to requests for access from a plurality of equipments operatively connected to a corresponding port of said apparatus. The requests for access have a plurality of command levels wherein the command levels have a fixed predetermined priority relative to each other. The apparatus comprises a plurality of port request control elements for generating a plurality of specific request signals including a command level request signal to indicate the command level of a request received from the corresponding equipment, and a go signal to indicate the availability of the apparatus and the subsystem in order to execute the command requested. An activity priority select control element receives the specific request signals, and processes the go signals from each of the port request control elements to grant access within a predetermined time period to the equipment connected to the port having the highest port priority within the highest command level.

Abstract: Apparatus for entering encoded data, command, and address information via a keyboard for transfer to an automated maintenance system designed to perform certain tests on or cause selected events in a unit of a data processing system such as the central processing unit. The data, command and address information entered via the keyboard by an operator serves to control the tests performed by or the events caused by the automated maintenance system. The maintenance panel also includes a plurality of display devices for displaying the data, command and address information sent to the automated maintenance system as well as data received by the automated maintenance system from the unit under test indicating the correctness of its performance. In the preferred embodiment, several LED indicators are also used for prompting and status indication.

Abstract: There is disclosed herein an apparatus for use in automated testing of elements in data processing systems such as the central processing unit. The system is comprised of a microprocessor with associated firmware, RAM and peripheral communications devices. There are two communication interface ports for receiving commands and instructions from local and remote computer terminals or from data processing units programmed to cause the testing apparatus to perform predetermined sequences of tests. There is also a port for connection to a portable maintenance panel which can be held in the hand of a field engineer for controlling the testing apparatus. The system is designed to replace prior art maintenance panels used for debugging computer hardware.

Abstract: Apparatus for use in coupling an automated maintenance system of general utility to a central processing unit of a data processing system. The interface apparatus is comprised of path control and operational condition control registers to control and enable the paths accessed by the automated maintenance system and to control the conditions of operation of the central processing unit. A control point register stores control point information from the central processing unit indicating its internal status. This information is read and displayed by the automated maintenance system. Address and data registers serve to buffer data and addresses exchanged between the automated maintenance system and the CPU. The disclosed interface apparatus allows a general utility automated maintenance system to be adapted to test a specific central processing unit.