IC 7486, XOR gate
An XOR (Exclusive – OR) gate is a digital logic with two or more inputs and one output that performs exclusive disjunction. The output of the XOR gate is HIGH (1) only when exactly one of its inputs is HIGH (1). If both inputs of a XOR gate are LOW (0), or if both inputs are HIGH (1) , then the output of the XOR gate is false. The symbol, truth table and the Boolean expression for XOR gate are below.
The 7486 IC package contains four independent positive logic XOR GATES. Pins 14 and 7 provide power for all four logic gates.
IC 74266, XNOR gate
Basically the “Exclusive-NOR Gate” is a combination of the Exclusive-OR gate and the NOT gate but has a truth table similar to the standard NOR gate in that it has an output that is normally HIGH (1) and goes LOW (0) when any of its inputs are HIGH (1).
However, the output goes HIGH (1) only when both of its inputs are at the same logic level, either binary “1” or “0”. For example, “00” or “11”. The truth table, equivalent circuits, Boolean expression and symbol for XNOR gate are below.
The commonly used IC for XNOR gate are the 74266 (Quad 2-input gate with open collector output) and 747266 (Quad 2-input XNOR gate). The IC comprises of four independent 2-input exclusive-NOR gates with open-collector outputs which can be used a 4-Bit digital comparator. The open-collector outputs permit tying outputs together for multiple-bit comparisons.
IC 7447, BCD to seven segment decoder/driver IC
7447 IC accepts a binary coded decimal as input and converts it into a pattern to drive a seven-segment for displaying digits 0 to 9. Binary coded decimal (BCD) is an encoding method in which each digit of a number is represented by its own binary sequence (usually of four bits). It accepts four lines of BCD (8421) input data and generates their complements internally. The data is decoded with seven AND/OR gates to drive indicator LEDs of the seven segment display directly. The outputs correspond to common anode (CA) configuration of seven segment. The pin out diagram and the pin description for IC7447 are shown below.
|BCD Input 2||A1|
|2||BCD Input 3||A2|
|3||Display test (Active low)||LT|
|4||Ripple blanking output (Active low)||RBO|
|5||Ripple blanking input (Active low)||RBI|
|6||BCD Input 4||A3|
|7||BCD Input 1||A0|
|9||Segment outputs; Active low||e|
|16||Supply voltage; 5V (4.75V – 5.25V)||
The datasheet for 7447 IC is available at 7447 IC.
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