7 segment to BCD converter

MSI and LSI chips as used in clocks, pocket calculators and the like are now being offered at surprisingly low prices. However, if they are intended for driving a display the readout infor- mation is often p`resented in multi- plexed seven-segment format. Decimal to seven-segment to BCD encoding logic, where an energised segment corre- sponds to logic `zero`. Only 5 out of the 7 available segment outputs are used, as shown in the diagram, since these are sufficient to produce the conversion to BCD code. This is all right for the display, but it is not much use for anything else. If a `normal` digital output is added, the field of application can be extended to include the use of a printer as well as other devices. What is required is a unit that will convert the seven-segment code into a binary coded decimal format (BCD). The BCD output will still be multiplexed, but this is easily remedied by adding a series to parallel converter (a shift register).