Abstract: The I/O configuration of a computer system includes two channels which are capable of being available on up to four interface ports, with the ports being incorporated within the channel in order to eliminate the need for an external switch. Control indicators are provided for monitoring the communications request initiation status of each channel and each port to achieve expeditious transfers through a selected port between the channel and peripheral devices. The I/O configuration is established responsive to the communications request initiation status that indicates one of several states depending on which side initiates a request and whether the connection has been made.

Abstract: The I/O configuration of a computer system includes two channels which are capable of being available on up to four interface ports, with the ports being incorporated within the channel in order to eliminate the need for an external switch. Control means are provided for monitoring the status of each channel and each port in order to achieve expeditious transfers through a selected port between the channel and peripheral devices. Error reporting is limited to the area directly affected by the error, and immediate disconnection helps to isolate the error and allow time for error recovery before the particular channel or port again becomes available.

Abstract: A system for ensuring accurate transmission of data between two functional units. A checking code generator is provided and a device operatively connected to the checking code generator ensures proper operation thereof.