DATA PROCESSING SYSTEM HAVING A COMMON CHANNEL UNIT WITH CIRCULATING FIELDS

摘要

A data processing system where transfers of information are made between I/O devices and system storage through channels is a channel unit having common apparatus shared among all the channels. The common apparatus includes a sequentially accessed state memory and a plurality of processors. The state memory includes a memory location for each channel. The processors have access to different parts of the state memory and perform functions in response to stored information. A data access processor controls transfers between system storage and the channel unit. A controller interface processor controls transfers between the channel unit and I/O devices. The quantity of information to be transferred for each channel is stored in the state memory. Each time a portion of the total transfer is completed, a count field in the state memory is updated. In one embodiment, only the low-order bits of the total count are stored in the state memory and the balance or high-order bits of the count are stored in channel memory.