Black Lives Matter - Action and Equality. ... Adafruit is open and shipping.
0

What explains the counter-intuitive numbering of chip pins? @CoolSWEng

Diomidis Spinellis helps explain why the pin numbering on chips is how it is:

One of the first things one learns in electronics is how chip pins are numbered. In the common dual in-line package (DIP) pin numbering starts from the left side of a notch appearing on the top of the package and continues counterclockwise until it reaches the other side of the notch. Why are pins counter-intuitively numbered in a rotating fashion rather than by columns as one would expect for a rectangular package? And why is the numbering not following the direction of a clock’s numbers? I think that both decisions can be traced back to history.

Before the advent of integrated circuit chips and transistors, electronic circuits were built using vacuum tube valves. In time simple three-pin diode valves evolved into more complex configurations with multiple pins, such as those for the plate (anode), one or more grids, the cathode, and the heater. As vacuum tubes are rather bulky it would be natural to number these pins while looking at them from their bottom side. Furthermore, to avoid mistakenly inserting a tube into a socket with the pins in the wrong order, many tube sockets, such as the octal one, introduced a key in the rib post to fit an indexing slot in the socket. This was naturally placed between the first and the last numbered pin. You can see both features in the picture above and the diagram below, which depicts the tube’s pins viewed from below.

Octal base vacuum tube numbering (7AK7)

Octal base vacuum tube numbering (7AK7)

Integrated circuits seem to have inherited this numbering scheme from vacuum tubes. If we look at a chip from underneath, its pins are numbered clockwise in a circular fashion, just as a tube’s would be. It gets better: the notch between the chip’s first and last pin (see picture below) corresponds to the tube’s key.

See how the chip takes after the tube in the blog post.


We are angry, frustrated, and in pain because of the violence and murder of Black people by the police because of racism. We are in the fight AGAINST RACISM. George Floyd was murdered, his life stolen. The Adafruit teams have specific actions we’ve done, are doing, and will do together as a company and culture. We are asking the Adafruit community to get involved and share what you are doing. The Adafruit teams will not settle for a hash tag, a Tweet, or an icon change. We will work on real change, and that requires real action and real work together. That is what we will do each day, each month, each year – we will hold ourselves accountable and publish our collective efforts, partnerships, activism, donations, openly and publicly. Our blog and social media platforms will be utilized in actionable ways. Join us and the anti-racist efforts working to end police brutality, reform the criminal justice system, and dismantle the many other forms of systemic racism at work in this country, read more @ adafruit.com/blacklivesmatter

Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.

Join 20,000+ makers on Adafruit’s Discord channels and be part of the community! http://adafru.it/discord

Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.

Join us every Wednesday night at 8pm ET for Ask an Engineer!

Follow Adafruit on Instagram for top secret new products, behinds the scenes and more https://www.instagram.com/adafruit/

CircuitPython – The easiest way to program microcontrollers – CircuitPython.org


Maker Business — To make it through a tough business cycle, layoffs should be a last resort

Wearables — Everything in its place

Electronics — The Case Of The Disappearing Capacitance

Python for Microcontrollers — Python on Microcontrollers Newsletter: New Hardware, Python Releases and Much More! #Python #Adafruit #CircuitPython @circuitpython @micropython @ThePSF

Adafruit IoT Monthly — BLE Store Capacity Indicator, Aquarium Automation, and more!

Microsoft MakeCode — MakeCode Arcade Game Garden Jam!

EYE on NPI — Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey

New Products – Adafruit Industries – Makers, hackers, artists, designers and engineers! — NewProducts 8/6/2020 Feat. #Adafruit #ST25DV16K I2C #RFID #EEPROM #Breakout – STEMMA QT / Qwiic!

Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at AdafruitDaily.com !



No Comments

No comments yet.

Sorry, the comment form is closed at this time.