Abstract: An input-output subsystem for the handling of data-transfer operations in a digital data processing system. The I/O subsystem provides a series of I/O controller-processors, designated as Line Control Processors, which are organized into groups to form a Base Module. A plurality of such Base Modules are organized to work with a main system interface unit called an Input-Output Translator which is part of the main host system comprising a processor and main memory. The Input-Output Translator (IOT) provides direct memory transfers to and from any connected Line Control Processor independently of the main processor. This arrangement simplifies the expansion of system capability for handling a greater number of peripheral devices on a simple economic basis while increasing data-transfer rates and reducing access errors in individual transfer operations.

Abstract: An Input-Output Interface Data-Transfer Control Unit, designated as a Line Control Processor, which provides the execution of instructions in accomplish data transfers between a main data processing system and a plurality of different types of peripheral devices. Further, said Line Control Processor provides for the buffering of at least two complete blocks of message data, thus to prevent access errors, since complete record length message transfers can occur in any given data-transfer cycle. The Line Control Processor operates with a standard communications and control discipline which makes the eccentricites of various types of peripheral units transparent to the main system. The Line Control Processor executes data-transfer instructions within the overall system thus relieving the central processor of an involvement in these tasks.