Expandable communication system using data concentration

Abstract

A communication system including one or more host adapters connected to a host computer, each adapter having multiple serial communication ports for transferring data between the computer and several TTY devices. Several of the adapter's serial ports include a high speed serial link for communicating with a data concentrator. The adapter automatically detects the presence of a concentrator connected to a switchable port and switches to the high speed link. Each concentrator includes multiple serial ports for communicating with TTY devices, and a high speed serial link for communicating with the adapter's high speed link. The concentrators allow more than one TTY device to share a single adapter serial port. Data from all of the TTY devices is accumulated into an adapter data buffer during a configurable time period or until a certain amount of data is accumulated, at which time the adapter interrupts the computer and transfers the accumulated data to the computer in one transfer operation. Likewise, the computer accumulates data for the TTY devices and transfers this data to the adapter in one transfer operation. Communication between the adapters and concentrators through the high speed serial communication link is implemented using a small fixed-size addressed packet to achieve a low overhead, high performance communications protocol. Each high speed link between an adapter and a concentrator is implemented to provide inherent flow control of data. The concentrators include a fail safe global flow control mechanism to prevent overflow of data from the TTY devices.