A single chip microcomputer has a parallel input-output port. The port comprises: an external input shift register with a parallel input port; an external output shift register with a parallel output port having a latch circuit; and a plurality of internal port units coupled in series to each other. Each of the plural port internal units comprises a data register and a shift register coupled to the data register, the data register being coupled to an internal bus. A serial input device couples the external output shift register with the shift register in the internal port unit existing at a terminal point of the internal port series; whereas a serial output device couples the external input shift register with each of the shift registers in the internal port units. A control circuit coupled to both the external input and output shift registers controls shift performances of the external input and output shift registers.

A method and apparatus providing remote access to server consoles in a network is disclosed. The method and apparatus provides remote access by utilizing a single server designated an access server, multiple serial port means attached to this single access server, and a plurality of additional servers coupled to this multiple serial port means. The method and apparatus couples the server console lines to the serial ports of the multiple serial port means as well as server console terminals. Remote access is accomplished by gaining access to the access server, which then provides access to any one of the serial ports associated with the access server, thereby providing remote access to any one of the plurality of server console lines coupled to the multiple serial port means. This capability is accomplished while local accessibility to the server console terminals is maintained.

A data switch interconnects a number of data processing nodes. The switch includes a number of port units for interfacing with the processing nodes, a number of multiplexing units for performing the switching, and a connection control unit. When a port unit wishes to initiate a connection, it sends a connection command over a command bus to all the multiplexing units and to the connection control unit, specifying a proposed data connection. Each multiplexing unit responds to the connection command by preparing the proposed data connection. At the same time, the connection control unit checks whether the proposed data connection is permissible. If it is permissible, the connection control unit then sends a GO signal to all the multiplexing units instructing them to complete the prepared connection.

A switching array as described for connecting ones of a plurality of data sources to ones of a plurality of data sinks. The array includes source data busses which transmit from a connected source, data words, a connection mask and a connection designator. The connection mask has bit positions that map to individual data sinks. A multiplexer/control circuit module is associated with each individual data sink for controlling the interconnection of the data sink to a source data bus. Each multiplexer/control circuit module is connected to each source data bus and is responsive to an active state connection mask bit and a connection designator on a first source data bus, to establish a connection between an associated sink and the first source data bus. This configuration enables the multiplexer/control circuit module to establish a connection without reference to any other multiplexer/control circuit.

A computer interconnect coupler has channel transmitters and channel receivers and logic circuitry for the routing of messages from the channel receivers which are addressed to the channel transmitters. When a message is received by a channel receiver, the channel receiver stores the beginning portion of the message in a first-in-first-out buffer, and sends a route message request to central switch logic. If the destination transmitter or receiver is busy, the central logic places the message request on a destination queue and returns a signal to the requesting source transmitter to turn on a flow control signal which is transmitted back to the data processing device having originated the message. Any message addressed to this data processing device, however, is inserted into the flow control carrier with pauses both before and after the message, and provisions are also made to allow the data processing device to return an acknowledgment responsive to the incoming message. To permit incremental expansion of the coupler to accommodate an increased number of channels, additional channel interface boards may be added. The coupler also includes a plurality of timers which determine fault conditions, and a diagnostic processor monitors the timers and associated error flags to diagnose faults to the board level. The conditions existing at the time of fault diagnosis are written into a non-volatile memory located on the circuit board. Therefore, the information is physically carried along with the board to the repair facility.