Multiplex communications – Wide area network – Packet switching
Patent
1991-09-27
1994-11-22
Bowler, Alyssa H.
Multiplex communications
Wide area network
Packet switching
395725, 395775, 395650, 370 859, 364230, 3642402, 3642646, 3642813, 364DIG1, G06F 1300
Patent
active
053676955
ABSTRACT:
A bus-to-bus interface preserves data coherence between masters and slaves operating within a multiple processor computer system. Two buses are connected via the interface. The first bus connects a number of self-identifying masters. The second bus connects a number of master devices and a number of slave devices. The second bus has no mechanism with which devices connected to the second bus may identify themselves. The interface contains a pair of registers for each slave device connected through the second bus. One register stores a busy bit if the corresponding slave is engaged on behalf of a master. The second register stores an identifying code for the master delegating a task to the corresponding slave. When a slave has accepted a task on behalf of a master and commanded the master to relinquish the bus, the busy register will be set and the master identification register will store the identifying code for the delegating master. Thereafter no master will be permitted to access the engaged slave unless the master identification code is that of the delegating master. Moreover, a delegating master will be denied access to the slave by that slave until the slave has completed the task accepted on behalf of the master. By preventing unintended masters from accessing slaves prior to the delegating master, inadvertent data transferred to the wrong master is avoided. Data coherence between master and slave is thereby ensured.
REFERENCES:
patent: 4191997 (1980-03-01), Luiz
patent: 4574350 (1986-03-01), Starr
patent: 4912633 (1990-03-01), Schweizer et al.
patent: 5115499 (1992-05-01), Stiffles et al.
patent: 5148545 (1992-09-01), Herbst et al.
Chen Sun-Den
Narad Charles E.
Bowler Alyssa H.
Shah Alpesh M.
Sun Microsystems Inc.
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