Method to Cause State Changes in Single Facility, Sub-Area or Entire Input/Output Hierarchy
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
This article describes a method used in the input/output I/O subsystem of a data processing system that causes state changes in a single facility, sub-area, or entire I/O hierarchy while preserving the view of immediate execution by the processor program. Fig. 1 depicts a multi-level I/O hierarchy. Such hierarchies are (Image Omitted) normally balanced with respect to addressability, but unbalanced in actual implementation. To accommodate unbalanced implementations, it is desirable to have the branch ends of the hierarchy, specifically the target devices of I/O commands, residing at different levels of the hierarchy. Therefore, an I/O address is provided which specifies at what level the end target resides. The I/O address is shown in Fig. 2.