Protected Jumper Fault Instrument
Original Publication Date: 1980-Apr-01
Included in the Prior Art Database: 2005-Feb-13
Some families of logic circuits have two types of signals, which are of interest here. The emitter-follower (EF) drivers switch between two negative values, such as -1 V and -2 V, while the open collector (OC) drivers switch between a negative value, such as -1 V, and ground. In both types, the net settles to the -1 V state when the driver transistor is turned OFF. In order to systematically apply known errors into a processor using such logic, signal I/O pins on each card are tied, with a temporary jumper wire, to one of two voltage levels depending on the driver type. Attaching the jumper to the wrong voltage could easily destroy the logic under test.