Peripheral interface system

Abstract

A peripheral interface system is disclosed. An input-output processor is provided to receive input-output commands from a central processing unit. Up to four multiplexing units may be connected to the input-output processor, with each multiplexing unit providing an interface for up to four controller units, which may be used to control a peripheral device. The multiplexing unit includes a pair of data buffers, each with its own addressing circuit, and each functionally divided into four storage areas, each storage area providing four registers to store four parcels of data. Data is transferred between the input-output processor and the controller units by filing the storage area in a buffer from the local memory of the input-output processor in a serial fashion over a DMA channel provided between the multiplexer and the local memory. Data transferred from the storage area in the multiplexer to a controller is sent one parcel every four clock periods, according to a scanner/time slot synchronization scheme between the multiplexer and the up to four controllers which may be connected thereto. Similarly, data parcels are transferred from the controller to the multiplexer on a scanner/time slot basis, and from the storage area of the multiplexer to the memory in a serial, consecutive fashion over the DMA channel. In operation, the buffers of the multiplexer are alternately filled and emptied such that one may be filling while the other one is emptying. A pair of buffers are also provided in the controller unit, which also may be alternately filled and emptied as between the peripheral device and the multiplexer.