I have both on stock: ATtiny861A-SU and ATtiny861-20SU.

But I can not find out any difference between them except 'In-System Programmable via SPI Port' available for 'A' version.

Could anyone tell me what is the difference between those two devices?



1 Answer 1


A-grade AVRs (and as of November 2014, B-grade AVRs) are minor improvements over the previous iteration; these improvements vary from chip to chip, e.g. the difference between ATtiny2313 and ATtiny2313A is different from the difference between ATmega128 and ATmega128A. Atmel has application notes that explain the difference.

AVR531: "Migrating from ATtiny261/461/861 to ATtiny261A/461A/861A"

  • \$\begingroup\$ Thank you for your answer and for the link provided! Now it's clear! \$\endgroup\$ Apr 4, 2014 at 7:59
  • \$\begingroup\$ Is there such a document for every μC? \$\endgroup\$ Feb 29, 2016 at 0:22
  • \$\begingroup\$ I'm not sure. There should be. \$\endgroup\$ Feb 29, 2016 at 0:29

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