Abstract: In a ring-structured data communication network, in which plural data processing systems exchange data and control information on a full duplex peer to peer basis, systems are presently architected to assign at least three I/O subchannels (i.e. at least three device addresses) to respective ring interface adapters. At least two of these subchannels are dedicated for providing separate input paths from the ring to at least two associated program-assignable areas in their system's main store, and a third of these subchannels is dedicated as an output path from the system's store to the ring. Collectively, these subchannels can sustain two input transfer processes and one output transfer process concurrently. One of these input processes is associatable with a locked mode of adapter operations which provides a non-blockable path for data transfer from a selected (remote) station on the ring to the respective system's main store.

Abstract: A method of initializing non-synchronous peer-to-peer data communication rings, and for effecting error recovery in such networks. On detection of error, each station operates in a purging configuration to clear the ring. In the purging configuration the station's receiving circuits are isolated and its transmitting circuits transmit "clear" signals containing this station's own address as destination. These signals serve to purge all potentially erroneous information in all upstream stations which then are operationally connected to that station. If a loss condition is persistent the station operates first in a "bypass" configuration for a third predetermined time interval, then in the purging configuration for the second time interval, and then resumes normal operation. In the bypass configuration the station's ring input is connected directly to its output and the (locally clocked) output of its transmitting circuits is connected to the input of its receiving circuits.

Abstract: For a system including a plurality of processors which are interconnected by a communications link through individual communication stations, a method of remote processor initialization is disclosed which provides a specific frame exchange procedure for the transmission of initial program load data from a source processor to an acceptor processor.All stations are basically equal. Provision is made in each station to automatically generate a Request Initialization Frame under certain conditions when the attached processor is an acceptor, and for transmitting initial program data transfer frames between a start and a termination frame, when the attached processor is a source. Each station can be set to indicate the type of the attached processor, and to handle initialization frames appropriately.