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Look-Ahead Contention Resolver for Bus Mastership

IP.com Disclosure Number: IPCOM000063148D
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18

Publishing Venue

IBM

Related People

Authors:
Awsienko, O Billingsley, RE Nahata, P [+details]

Abstract

A technique is described whereby a look-ahead method is used to control input and output (I/O) bus mastership. The method used resolves contention problems by using minimum hardware and in only one clock cycle. Most contention problems are solved by serial polling the bus, and determination of mastership is based on the priority level established by each I/O bus. A typical priority level is shown in Table 1 where priority request lines are listed in descending order of priority along with their corresponding bit patterns. Depending on the bit pattern, it is possible for the I/O bus to have any one of eight states, as shown in Table 2, along with the internal state of the lines being outputted by the internal I/O bus.