I've bought this microSD reader/writer: http://www.ebay.com/itm/131132034753

I've found only one tutorial, where the pins are similar to my pins, but in the example there is a CLK instead of SCK: https://learn.sparkfun.com/tutorials/microsd-shield-and-sd-breakout-hookup-guide

The pins on my MicroSD reader are:

  • CS
  • SCK
  • MOSI
  • MISO
  • VCC
  • GND
  • 3
    SCK is actually a clock signal. So basically, they are the same thing here.
    – Ikbel
    Nov 16, 2015 at 22:42

2 Answers 2


SCK stands for SPI ClocK

CLK stands for SPI CLocK

Two different acronyms for the same thing.


It's common practice for speakers/writers to use the generic term: "clock" (CLK) for various different situations. This clearly being a serial interface we don't need to specifically say Serial cloCK each time the signal mentioned, as it's more of a mouthful than saying "clock".

In this case consider "CLK" and "SCK" as fully interchangeable.

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