Level-Sensitive Interrupt for a Parallel Printer Interface Using Data and Status I/O for Reset
Original Publication Date: 1988-Apr-01
Included in the Prior Art Database: 2005-Feb-15
This article describes an interrupt arrangement which allows a compatible printer interrupt service in a system that uses level- sensitive interrupts and software that does not always check status. In a level-sensitive interrupt system, the interrupt must be removed from the bus before the interrupt service routine returns. In an edge-sensitive system, the only requirement is that the signal level must return sometime before the next edge. Some computers rely on the printer to directly control the interrupt line via the -ACK line. This slow method is satisfactory in edge-sensitive systems, but, in a level sensitive system, a faster means of acknowledging the interrupt at the adapter is needed rather than waiting on the printer.