DM8899

DM8898 DM8899 TRI-STATE BCD to Binary Binary to BCD Converters January 1987 DM8898 DM8899 TRI-STATE BCD to Binary Binary to BCD Converters General Description These circuits are the TRI-STATE versions of the popular BCD to binary and binary to BCD converters DM74184 and DM74185A respectively They are derived from the 256-bit ROM DM8598 Emitter connections are made to provide direct read out of converted codes at outputs Y8 through Y1 as shown in the truth tables Both converters comprehend the fact that the least significant bits (LSB) of the binary and BCD codes are logically equal and in each case the LSB bypasses the converter Thus a 6-bit converter is produced in each case and both devices are cascadable An overriding enable input is provided on each converter which when taken high inhibits the function causing all outputs to go into the high-impedance state For this reason and to minimize power consumption unused outputs Y7 and Y8 of the 185A and all ‘‘don’t care’’ conditions of the 184 are programmed high DM8898 BCD-TO-BINARY CONVERTERS The 6-bit BCD-to-binary function of the DM8898 is analogous to the algorithm a Shift BCD number right one bit and examine each decade Subtract three from each 4-bit decade containing a binary value greater than seven b Shift right examine and correct after each shift until the least significant decade contains a number smaller than eight and all other converted decades contain zeros In addition to BCD-to-binary conversion the DM8898 is ...