Browse Prior Art Database

Dynamic Priority Manager Under Application Program Control

IP.com Disclosure Number: IPCOM000043614D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Couder, A: AUTHOR [+3]

Abstract

To control the data stream between a control unit and its adapters on a common bus, priority has to be given to the requestor adapter with the highest priority. The priority level of any adapter can be changed at any time. This priority level is under control of the application program so that no manual intervention is required to change the priority. The dynamic priority manager is used to control the data stream between a host system and high speed scanners (HLS). The interface between the host system and the scanners is performed by a parallel data adapter to byte bus converter (PDA/BBC) interface which controls the HLS priority. When an HLS requests to interface PDA/BBC a transfer to the host system, this request is serviced immediately if interface PDA/BBC is available.

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Dynamic Priority Manager Under Application Program Control

To control the data stream between a control unit and its adapters on a common bus, priority has to be given to the requestor adapter with the highest priority. The priority level of any adapter can be changed at any time. This priority level is under control of the application program so that no manual intervention is required to change the priority. The dynamic priority manager is used to control the data stream between a host system and high speed scanners (HLS). The interface between the host system and the scanners is performed by a parallel data adapter to byte bus converter (PDA/BBC) interface which controls the HLS priority. When an HLS requests to interface PDA/BBC a transfer to the host system, this request is serviced immediately if interface PDA/BBC is available. If not, the HLS stacks its request for further processing. So, while interface PDA/BBC is busy, several HLS may be waiting for message transfers. As soon as interface PDA/BBC becomes idle, only one HLS is serviced, namely the one whose message has the highest priority. Priority is determined according to different criteria, such as: . Type of message . Speed of teleprocessing line

. Time during which this message is waiting,

etc. under application program control.

Consequently, the priority of a specific message waiting for transfer may evolve with time from non-urgent to urgent status. Priority is managed at two levels: inside the HLS where it is determined which message has the highest priority among several waiting messages and inside interface PDA/BBC to determine which HLS has the message with the highest priority. To do this function, when interface PDA/BBC becomes idle, it polls all HLS to get their highest waiting message priority and give control to the highest priority requestor. The dynamic priority manager comprises four logic subfunctions: 1.

Priority sequencer which is a logic unit under PDA/BBC interface control which manages all dynamic priority

manager subfunctions. 2. Transit request bit (TRB) checker and HLS request table. The checker is a logic unit which reads the byte...