Exculsove NOR LOGIc

the XNOR gate (sometimes spelled "exnor" or "enor") is a digital logic gate whose function is the inverse of the exclusive OR (XOR) gate. The two-input version implements logical equality, behaving according to the truth table to the right. A HIGH output (1) results if both of the inputs to the gate are the same. If one but not both inputs are HIGH (1), a LOW output (0) results.

XNOR Gates are basic logic gates, and as such they are recognised in TTL and CMOS ICs. The standard, 4000 series, CMOS IC is the 4077, which includes four independent, two-input, XNOR gates. The pinout diagram is as follows:

This device is available from most semiconductor manufacturers such as NXP. It is usually available in both through-hole DIP and SOIC format. Datasheets are readily available in most datasheet databases.

If no specific XNOR gates are available, one can be made from four NOR gates or five NAND gates in the configurations shown below. In fact, any logic gate can be made from combinations of only NAND gates or only NOR gates.