SR

In the context of an Embedded system, SR usually stands for status register. The status register is a CPU register which consists of a collection of flags and settings. Which flags and which settings depends very much on the CPU.

Flags

Which Flags a CPU depends. However, there are a number of flags which most CPUs have, such as: Z-Flag Zero Flag. Indicates if the result of the previous operation has been 0 C-Flag Carry Flag. Typically used in shift and rotate operations, as well as in addition and subtraction. I-Flag Interrupt enable Flag. Enables (or disables) interrupts. Note that this flag is not so much standard as Z and C