INTERCHANGEABLE INTERFACE CIRCUIT STRUCTURE

The present structure is an interchangeable interface circuit card which per se includes: circuitry which is responsive to being addressed in accordance with its physical location; circuitry to generate signals which identify the circuit being addressed and the peripheral to which it is connected; and circuitry to generate signals which effect a diagnostic routine applicable to at least some of the interchangeable interface circuits on the circuit card being addressed. In addition the present structure includes priority circuitry which operates in conjunction with a data handling system to assert a priority value assigned to the interchangeable interface circuit card and which, based on that priority, determines which one of a number of interchangeable interface circuit cards will be permitted to control a common data path.