embeddedmicrocontrolleratmegaavr-gccatmega32

EICRA - External interrupt control register "A"?

while learning about the external interrupts, I have gone through the document of atmega328p. came across EICRA, why is that it is necessary to explicitly mention as A, when there isn't anything called EICRB(using ctrl+f, I have searched for EICRB in the document).

Solution

  • Because other models may have more external interrupt capable pins and may need more control registers. This naming approach provides forward compatibility (to some extend) with more capable products.

    For example, take a look at ATmega2560 datasheet. You will notice that it has EICRB, as well as more bits in EICRA compared to ATmega328P.