BCD-8421-code serial tetrade adder and subtractor - includes BCD and=or, and BCD-plus-6 to decimal decoders

摘要

A serial tetrade adder and subtractor operating in BCD-8421 code has an arithmetic unit in the form of a tetrade adder and a tetrade subtractor or a switchable tetrade arithmetic unit. Prior to each first addition in each decimal location, the base number 6 (LHHL) is added in and before each first subtraction in each decimal location the base number 6 is removed by subtraction prodded that the numerand is an addition result. The arrangement includes a BCD to decimal decoder circuit. The display involves first removing the base number 6 from each decimal location by subtraction. Alternative arrangement involve BCD plus 6 to decimal decoder circuits and a mixture of BCD to decimal and BCD plus 6 to decimal decoder circuits.