Patent GB-1306702-A (GB)
Title: Methods and devices for comiling a fault dictionary
IPC: G06F11/22
Filed: 1970-02-12
Abstract: 1306702 Testing computers HONEYWELL INFORMATION SYSTEMS ITALIA SpA 12 Feb 1970 [12 Feb 1969] 6881/70 Heading G4A [Also in Division H3] In a method of preparing a fault dictionary for an electronic apparatus, e.g. a digital computer, including internal input and output storage means and means for indicating to an observer the states of the output storage means (a) circuit alterations each simulating a single fault within the apparatus are sequentially made; (b) a diagnostic sequence of signals is applied to the apparatus concurrently with the simulation of each single fault, these signals being divided notionally into blocks; and  (c) at the end of every block of diagnostic signals if the states of the output storage means differ from their expected states, they are recorded, together with the corresponding block number (this composite record being referred to as a " symptom ") so that at the end of a complete pass of the diagnostic sequence of signals for each single simulated fault, a list of single faults and the symptoms produced by each of them will be obtained, which list may be inverted to list possible faults against each different symptom, said inverted list being referred to as a " fault dictionary ". Fault simulation.-It is assumed that although the apparatus under test may be large it only contains a small number of different types of printed circuit boards each carrying a small number, e.g. five, of different types of integrated circuit units. Typical such units are described (Figs. 2 and 3, not shown). For each different type of circuit board a substitute board 49, Fig. 15, is prepared having a combined plug 54 and socket 50 in place of each circuit unit that would normally be soldered to the board. In use, in order to simulate a single fault, an appropriate circuit unit 53 is plugged into every socket 50 except one, to which is attached, by means of the plug pins 54 and a socket 57, Fig. 16, a special unit 55, which may be controlled (by circuitry outlined in Fig. 17, not shown) to simulate the possible faults in the circuit unit it replaces. Operation of preferred embodiment.-In the preferred embodiment the compilation of a fault dictionary for a computer 1, Fig. 20, is supervised by a pilot computer 160 which stores a diagnostic program on a first magnetic tape 164, and records faults, and the symptoms they produce, on a second magnetic tape 165. The pilot computer also has a pack of punched cards 163, each of which corresponds to a single fault that is to be simulated in the main computer. Once the system is set in operation, the first card 163 is read and the pilot computer prints out 162 an operator instruction station which printed circuit board is to be replaced by one of the special boards, and which circuit unit, on the board is to be replaced by a special fault simulating unit. Once this is done, the diagnostic program 164 is run to check that no faults are present. An operator instruction is then printed out calling for a specified fault to be simulated by the fault simulating unit. The diagnostic program is then run again and the resulting fault symptoms are recorded 170. This process is repeated until every fault listed in the card pack 163 has been simulated and evaluated. Finally the record 165, which list faults and the symptoms they cause, can be processed by the pilot computer to produce the required fault dictionary. The Specification does mention that it is not necessary to use a pilot computer: instead each block of the diagnostic program could be recorded on a punched card, and the computer can be arranged that cards are read and obeyed sequentially until an incorrect result is obtained whereupon card reading is stopped so that the operator can note the incorrect result and the block number causing it, before pressing a " go " button causing further card reading.