74LS85 4-Bit Magnitude Comparator IC (7485 IC) DIP-16 Package These 4-bit magnitude comparators perform comparison of straight binary or BCD 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 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 path is implemented with only a two-gate-level delay to reduce overall comparison times for long words.

What is a 4-bit Magnitude Comparator?

A 4-bit magnitude comparator compares two binary numbers each of four bits. It consists of eight inputs each for two four bit numbers and three outputs to generate less than, equal to and greater than between two binary numbers.

The 74LS47 accepts four lines of BCD (8421) input data, generates their complements internally and decodes the data with seven AND/OR gates having open-collector outputs to drive indicator segments directly. Each segment output is guaranteed to sink 24 mA in the ON (LOW) state and withstand 15V in the OFF (HIGH) state with a maximum leakage current of 250 µA. Auxiliary inputs provided blanking, lamp test and cascadable zero-suppression functions.

The 74LS245 octal bus transceivers are designed for asynchronous two-way communication between data buses. The control function implementation minimizes external timing requirements. The device allows data transmission from the A Bus to the B Bus or from the B Bus to the A Bus depending upon the logic level at the direction control (DIR) input. The enable input (G) can be used to disable the device so that the buses are effectively isolated.

The 74LS194 bidirectional shift register is designed to incorporate virtually all of the features a system designer may want in a shift register; they feature parallel inputs, parallel outputs, right-shift and left-shift serial inputs, operating-mode-control inputs, and a direct overriding clear line. The register has four distinct modes of operation, namely: Parallel (broadside) load Shift right (in the direction QA toward QD) Shift left (in the direction QD toward QA) Inhibit clock (do nothing) Synchronous parallel loading is accomplished by applying the four bits of data and taking both mode control inputs, S0 and S1, HIGH. The data is loaded into the associated flip-flops and appear at the outputs after the positive transition of the clock input. During loading, serial data flow is inhibited. Shift right is accomplished synchronously with the rising edge of the clock pulse when S0 is HIGH and S1 is LOW. Serial data for this mode is entered at the shift-right data input. When S0 is LOW and S1 is HIGH, data shifts left synchronously and new data is entered at the shift-left serial input. Clocking of the flip-flop is inhibited when both mode control inputs are LOW.