History Lesson 4017 pin order

Discussion in 'General Electronics Chat' started by FiberWeave, Sep 8, 2008.

  1. FiberWeave

    Thread Starter New Member

    Sep 8, 2008
    Why on chips like the 4017 decade counter are the order of the output sequence not in pin order? The 4017 counts 1-10 but the output pin order is 3, 2, 4, 7, 10, 1, 5, 6, 9, 11.

    I etch my own boards and I can never get a good layout on a single sided board without jumpers. I have the same problems with seven segment displays.

    Just wondering if anyone knows why certain chips have pins orders that I can't easily map to their counter part? What the history behind it?:confused:
  2. SgtWookie


    Jul 17, 2007
    It's because the IC designers were a sadistic lot back then. ;)

    Seriously though, the CMOS 4000 series were introduced by RCA in 1968. 40 years ago, design work for ICs was done using hand-cranked calculators, and drafting tables. There was no such thing as a "personal computer" back then; access to "mainframe" computers was very limited. It's quite remarkable that the designers of the time came up with components so useful that they are still widely used today.

    Here's an informative link:
  3. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    You're right about 7-segment displays, I can't think of a worse arrangement. Why couldn't they put all the pins in a vertical line so they could all be bussed together for multiplexing. I mean, they are almost always multiplexed:confused:

    Annnnd, I know there may be historic reasons but why are they still the same now?
  4. SgtWookie


    Jul 17, 2007
    I guess they figured the engineers using the ICs would sort out half the mess at one end, and the other half of the mess on the other end :)

    Changing the pinout on the IC could've been done, I suppose - could be merely a matter of connecting the die to the carrier differently. However, that might require re-tooling or some such; at least re-programming of the wire bonder.

    No matter WHAT pinout they used for a new version, at least half of the users would scream bloody murder that the pinout was exactly the opposite of what they needed. They couldn't use the same part number, or it would cause pandemonium for those doing repairs.

    That's one of the big reasons why uC's are so popular nowadays - you largely get to choose which pins perform which functions. It sure is easier swapping the pins around via software than it is via hardware mods.