Part

74HC86 quad XOR

Four XOR gates.

or see every part
  • 14 pins
Drawn live by the editor's own code, at the size you see it.
Reference

Every one of its 14 pins

Pin
Role
What it does
1A
Input
1B
Input
1Y
Output
2A
Input
2B
Input
2Y
Output
GND
Input or output
3Y
Output
3A
Input
3B
Input
4Y
Output
4A
Input
4B
Input
VCC
Input or output
This part

What it does

The 74HC86 packages four independent two-input XOR gates in one 14-pin chip, wired the same pin layout as the 74HC00: pin 14 is VCC, pin 7 is GND, and both have to be wired before any gate does anything. An XOR has no controlling value the way an AND or OR gate does, since either input alone can flip the answer, so an unknown on either input gives an unknown output regardless of the other input’s level. That makes it the odd one out among the logic families Mokxi models, and it is also what makes an XOR the natural core of a binary adder’s sum bit, or of a simple parity check across several inputs. The same 9 nanosecond typical propagation delay applies here, inertially, so a pulse narrower than that time never reaches the output. Wired next to a 74HC00, as it is on the logic gate simulator page, the two chips answer the same two inputs completely differently, which is the whole point of showing them side by side.

How it is modeled

What is true about the 74HC86 quad XOR, here

74HC86: quad 2-input XOR gate

The 7486, same package, four exclusive-OR gates: the adder and parity building block, and the cheapest way to make a controllable inverter. An XOR has no controlling value, so any unknown input gives an unknown output. It sits one gate deeper inside the package than a NAND, so it is slower: propagation delay 12 ns typical. See it in: Full adder.

Not modeled

One typical delay, and nothing around it. Each chip carries a single propagation delay taken from its datasheet's typical column at VCC = 5 V, CL = 15 pF and 25 °C, and uses it for every path through the package. There is no minimum or maximum, no spread between the gates in one chip, no rise or fall time, no output slew and no dependence on supply voltage, load capacitance or temperature, all of which a real 74HC part has, and all of which a datasheet gives ranges for. On the 74HC595 the one figure is the STCP-to-Qn number used for SHCP and MR to Q7S as well, which the datasheet lists a nanosecond or two apart.

No setup, hold or pulse-width checks. The 74HC74 and the 74HC595 take a clock edge whenever they see one; nothing here refuses data that changed too close to the edge or a clock pulse that was too narrow, and nothing warns about it. A real part would metastable or simply miss.

No supply current, no output current limit and no bus contention damage. An output driving into another output is resolved as two drivers on one net; nothing gets hot.

Sequential parts power up cleared rather than random, because a toggle divider fed Unknown never escapes it. See how faithfully a part behaves.

From The 74HC logic family, in full.

Projects

See the 74HC86 quad XOR in a project

Learn

Where it turns up in a lesson

In the twelve week course

In a learn article

Wire up the 74HC86 quad XOR

Open the editor and push it into the breadboard. It is free, and it runs on your own machine.