TI SN74LS85DR

These 4-bit magnitude comparators can perform comparisons of straight binary and straight BCD (8-4-2-1) codes. Three fully decoded decisions about two 4-bit words (A, B) are made and are externally available at three output ports. These devices can be expanded to any number of bits without external gates. Longer words can be compared by cascading comparators. The A>B, A<B, and A=B outputs of the stage handling less significant bits are connected to the corresponding A>B, A<B, and A=B inputs of the stage handling more significant bits. The stage handling the least significant bits must have a high-level voltage applied to its A=B input. The cascading paths of the '85, LS85, and 'S85 are implemented with only two gate levels of delay to reduce the overall comparison time for long words. A cascading arrangement for further reducing comparison time is shown in the typical application data.