Hughes Microelectronics Limited

Hughes Microlectronics Limited

Kenelm G Murray

Gary L Dodd

Daniel H Bennett

Colin W Edwards

Philip Woodhead

A counter includes an array of memory cells arranged in groups of memory cells, each group designating a counting decade, wherein each group of memory cells includes first and second word strings, each capable of storing a data word, and a fault flag, capable of indicating which word string contains the data word; sensing means coupled to the memory array for checking the status of the memory cells and for generating fault signals upon detection of a fault in a memory cell; logic means coupled to the memory cells and to the sensing means for selecting the first or second word string in response to a fault signal; wherein upon detection of a fault in a first word string, the data word is written into the second word string; and a central shifting unit coupled to the memory array for reading a data word stored in a word string into the shifting unit, incrementing the data word, and writing the incremented data word into its respective word string.

Non-volatile counter employing memory cell groups and fault detection

A memory cell comprising a bistable latch having first and second nodes, at least two non-volatile transistors (NV1, NV2) each having a source, a drain and a control gate, the control gates being connected to the first node (NODE 1) and one of the source and drain of each transistor being connected to the second node (NODE 2), each non-volatile transistor (NV1, NV2) further having a substrate and a floating gate between the control and the substrate, and switching means (N1, N2, TG1) for enabling the transistors to be checked in circuit.

Non-volatile RAM bit cell

Counter circuit apparatus which sequentially re-allocates lower-order counting operation in order to extend counter life. The counter is comprised of a plurality of lower order counters and at least one higher order counter. A count selection circuit is coupled to the plurality of counters which controls the counting thereof in response to applied event input signals. A map control circuit is coupled between the higher order counter and the count selection circuit which controls the count selection circuit in response to signals derived from the higher order counter. The map control circuit sequentially enables a predetermined one of the lower order counters to count individual ones of the applied event input signals. A count unscrambling circuit is coupled to the plurality of lower order counters and the map control circuit which produces an ordered count output signal that is indicative of the number of event input signals counted by the counter. The operating lifetime of the counters is increased utilizing the principles of the present invention. One application of the present invention is that of a non-volatile up counter suitable for an odometer application. A counting method which provides for extended counter life is also disclosed.

Non-volatile counting circuit and method which provides for extended

Memory circuits having a floating gate transistor as a non-volatile storage element are constructed with a shunt transistor across the floating-gate transistor which in the event of a short circuit between the floating gate and the transistor substrate causes the memory to go into a predetermined fail-safe condition. The circuits are cross-coupled flip-flops with a driver and a complementary driver or load connected in series in each of the circuits, one driver or complementary driver or load being a floating gate transistor such as a FATMOS. Short circuiting of the floating gate to the control gate of the floating-gate transistor gives the same fail-safe condition.

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Chiddingfold, United Kingdom

Kenelm G Murray