Hughes Microelectronics Limited

David J Warner

An electronic counter such as for use in the odometer of a motor vehicle is provided comprising an array (10) of m rows and n columns of single flip-flop data latches and a central shifting unit (14). The central shifting unit (14) comprises a row of n data latches arranged to read data from and write data to each of the m rows of data latches of the array (10). In operation, the central shifting unit (14) reads data from a row of data latches of the array, performs a shift operation on the data and an invert operation on one of n data latches of the central shifting unit (14) and returns the data so operated on to the row of data latches in the array (10). By these steps, a counting operation in Johnson code is performed on the data. This invention uses less chip area than known counters.

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Weybridge, United Kingdom

David J Warner