Variable INTERRUPT PRIORITY Based on Last Device Serviced
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
In many computer systems it is necessary to attach a number of slave devices to a master device. Each slave device must request service from the master using an interrupt line. The goal is to allow the master to respond to an interrupt as fast as possible while ensuring that no slave is continually given priority over another device. Priority is assigned to an interrupt based on which device was last serviced. Each interrupt line is given a number or address. The address of the last device serviced is stored in a register. The address in this register is used by the interrupt priority logic to alter the priority given to each of the interrupts that are active. Lowest priority is given to the interrupt whose address is stored in the register. (This is the last interrupt which was serviced.