
A diagnostic circuit is used to test the operation of a complex digital system by transferring operands to and from a plurality of registers (12, 14, 16). In a typical application the registers (12, 14, 16) in operation utilize parallel data transfers. For diagnostic purposes the registers (12, 14, 16) are connected serially and, in response to selected shift commands, data can be shifted either right or left through the registers (12, 14, 16). First and second buses (18, 20) provide serial, bid...











