Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
In contemporary data processing systems, certain communications between I/O channels and device control units must be conducted within a "critical time" period. When this period is exceeded, the operation terminates abnormally in an overrun, requiring the central processing system to undertake lengthy analysis and recovery procedures which interfere with central processing productivity. This is particularly true, for instance, in respect to the transmittal of certain chained channel command words (CCWs) from channels to device control units where a time dependency exists between the performance by a control unit of operations specified by successive CCWs of a chain. A technique described presently ensures timely transmittal of such time-interdependent chained CCWs over standard channel to control unit interfaces.