Stack Implementation of Error Recovery and Device Interleaving
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Error recovery and program interleaving achieves multiple control by a by a programmable device controller. There are three types of device commands which can be issued by a controller. An immediate command completes quickly and is used to instruct the device hardware. An example is a reset command. An extended nondata command requires a significant amount of time to complete. An example is a disk seek or a tape rewind. An extended data command requires a significant amount of time to complete as well as constant usage of some system resources, for example, to transfer a line of print to a printer. Extended commands cause interrupts to the controller program when they terminate. The device controller program is broken down into two levels of routines.