These four-bit magnitude comparators perform comparison 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 outputs.
These devices are fully expandable to any number of bits without external
gates. Words of greater length may be compared by connecting comparators in
cascade. The A > B, A < B, and A = B outputs of a stage handling less-significant
bits are connected to the corresponding A > B, A < B, and A = B inputs
of the next stage handling more-significant bits. The stage handling the least-significant
bits must have a high-level voltage applied to the A = B input. The cascading
paths of the '85, 'LS85, and 'S85 are implemented with only a two-gate-level
delay to reduce overall comparison times for long words. An alternate method
of cascading which further reduces the comparison time is shown in the typical
application data.
These four-bit magnitude comparators perform comparison 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 outputs.
These devices are fully expandable to any number of bits without external
gates. Words of greater length may be compared by connecting comparators in
cascade. The A > B, A < B, and A = B outputs of a stage handling less-significant
bits are connected to the corresponding A > B, A < B, and A = B inputs
of the next stage handling more-significant bits. The stage handling the least-significant
bits must have a high-level voltage applied to the A = B input. The cascading
paths of the '85, 'LS85, and 'S85 are implemented with only a two-gate-level
delay to reduce overall comparison times for long words. An alternate method
of cascading which further reduces the comparison time is shown in the typical
application data.