Input/Output Control Block Indirect Device Control Parameter Mechanism
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
This article describes a technique for use in the input/output (I/O) subsystem of a data processing system which eliminates device dependencies in an I/O control block. The drawing illustrates a representative set of essential I/O command parameters for starting an I/O operation. The sizes of fields chosen for the illustration are arbitrary. The parameters are: .The command byte; The I/O address, showing a field for specifying up to four main; I/O busses which may be attached to a processor, and a field for specifying the address of the target device. A storage address, pointing to an I/O control block (IOCB) in the; main storage of the processor. These parameters are passed to the specified device on the appropriate I/O bus, and are called the immediate command parameters (ICPs).