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this could be most stupid question but i couldnt find where is the first pin: http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-11157-32-bit-Cortex-M4-Microcontroller-SAM4E16-SAM4E8_Datasheet.pdf

enter image description here

there is circle which identify pin 1, but is the pin on left or bottom side ???

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Pin 1 is the left most pin of the bottom in your image. Similar to the image below.

enter image description here

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  • \$\begingroup\$ so i always have to put the index cornet at "top left" and the pin 1 would be in the left anti-clock wise? \$\endgroup\$ Jul 30, 2018 at 14:53
  • \$\begingroup\$ You can orient the chip as you see fit. In relation to the index dot or circle, pin 1 will always be anti-clockwise. \$\endgroup\$ Jul 30, 2018 at 14:55
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    \$\begingroup\$ Do note that you cannot rely on the writing orientation - only the index mark. In this case the writing happens to coincide with how the chip is often oriented in a pin numbering diagram, but it others the writing will be rotated. \$\endgroup\$ Jul 30, 2018 at 15:39
  • \$\begingroup\$ @ChrisStratton - I once had a pc board with a dozen SMD instrumentation amps. The label and a beveled edge were BOTH opposite the orientation shown by the index mark. Fortunately, there were enough chips to share the reversed power supply polarity, and none of the ICs were damaged. They still had to be reinstalled, of course, but I could test the board function while replacements were being ordered. \$\endgroup\$ Jul 30, 2018 at 16:29
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Typically, it is customary to count pins counter clock-wise from the indicator pin. From that image, I would suggest that Pin 1 is the far left pin on the bottom.

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