International Business Machines Corporation

Richard H Waller

Jean L Calvignac

Bernard Brezzo

Kenneth T Wilson

Bernard J Naudin

Jean-Pierre Lips

Pierre Austruy

Edwin L Tucker

This invention relates to a protocol implemented in a communication system for exchanging data and control messages between adapters to which are attached different users, and a shared memory subsystem comprising a depository storage, a manager of storage and a microprocessor. Such protocol enables the adapters to be the initiators of the transmission and reception of data by using the control lines that connect the manager of storage to all adapters in the same way as the data bus and the address bus. Moreover, the adapters slice the messages into data bursts to which are associated control words specifying the sizes, the owner and the position of the burst in the message. Consequently, those data bursts may be interleaved when transiting on the data bus without the intervention of the microprocessor for the routing, and they will be stored in or read from the depository storage according to the identification of the user in the control word. Therefore, only the shared memory needs to have a high capacity of storage, whereas the manager of storage and the adapters can operate with a reduced capacity of storage, and the time to send or to access a data burst is much more improved.

Method for exchanging messages between a shared memory and communication

A reconfigurable serial loop or ring communication system is provided with a method and apparatus which enables stations on the loop to ascertain the address of its nearest active upstream neighbor (NAUN). A Ring Poll Frame is generated and broadcast from an originating station. The Ring Poll Frame includes a Ring Poll command, a From Address and a reset Address Recognized (AR) control bit. The first active downstream station recognizes the command with the control bit in the reset state, copies the contents of the ring poll frame and sets the bit. The set bit inhibits subsequent downstream stations from copying the frame. The first active station then generates a substantially similar formatted ring poll frame and passes it downstream. The process is continued by downstream active stations until the originating station receives a ring poll frame having a reset control bit. The reset control bit is an indication that all stations on the loop know the address of its NAUN. A ring management station may use the ring poll process to acquire information relative to the location of active stations on the ring.

Protocol for determining physical order of active stations on a token

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Chapel Hill, NC, United States of America

Richard H Waller