I/O data processing system.

摘要

A data processing system includes a communication subsystem having an I/O microprocessor for communicating with a central processing unit and a main memory; and a line microprocessor for communicating with a number of devices. The I/O microprocessor and the line microprocessor communicate with each other through mailboxes stored in a shared memory 44. The line microprocessor is controlled by a PROM 58 and channel control programms (CCP's) in a RAM 60, and uses a work RAM 52 for data storage; the I/O microprocessor is controlled by a PROM 38 and uses a work RAM 40 for data storage. The line microprocessor interrupts the I/O microprocessor to process data bytes being transferred between main memory and a device requesting service when the line microprocessor has responded to the requesting device and loaded the mailbox.