Interactive IC Pinout & Datasheet Quick-Finder

A pinout is only useful if you can hold the chip the right way round and tell a power pin from a signal pin. The diagrams above follow the convention every datasheet uses, and the colour groups are there so you can spot the supply and bus pins at a glance before you reach for a probe.

Orienting a DIP

On a DIP package, pin 1 is marked in two ways that should agree: a small dot moulded into the top of the case next to pin 1, and a semicircular notch cut into the top edge. Hold the chip with the notch uppermost and pin 1 is on your left; numbering then runs anticlockwise, down the left side and back up the right. If the dot and the notch disagree, trust the notch — a re-marked or counterfeit part can have a stray dot, but the notch is part of the moulding. The diagrams here draw the notch on the top edge and pin 1 at the top-left, exactly as you would hold the real part.

What the colours mean

Every pin is coloured by its function so the supply and bus structure stands out. Red is power, grey is ground, amber is a clock or timing pin, blue is the address bus, green the data bus, purple a control line, cyan general I/O, pink an analogue pin, and a muted grey marks a no-connect. The legend above the diagram lets you isolate one group at a time — useful on a 64-pin part where the address and data buses otherwise dominate the picture.

Why bus pins are grouped

The address, data and control pins are coloured as groups rather than individually because on a CPU they behave as groups: the address bus drives memory together, the data bus reads and writes together, and the control strobes fire in a fixed sequence. When a board faults, it is rarely one pin — a stuck address line usually means a shorted decoder or a dead buffer upstream, and a floating data bit often points to a failed transceiver, not the CPU. Grouping the colours makes those patterns visible.

Testing suspect logic in circuit

Before lifting a chip, probe it in circuit. Check the supply pins first — a gate with no VCC or a CPU with a missing clock will look dead and is usually not the chip's fault. On logic, drive an input and watch the output; a totem-pole output that never pulls low or high has a failed transistor, and an open-collector pin that stays high regardless of its input has lost its pull-up. On a CPU, scope the clock and the reset line, then the address bus during a reset fetch; a bus that never toggles points to a stuck peripheral holding the line, which is far more common than a dead CPU. Only when the supplies, clock and bus activity all look correct is the chip itself the prime suspect.