The Frame

Although we can use the registers to facilitate the communication between a caller and the called subroutine, registers are limited. There are only 32 registers with the AVR architectures. As a result, using registers to pass information is not sufficient in some cases.

Passing information via registers does have certain advantages. For example, registers are easy to set up and they do not require any memory space. Furthermore, access registers is easy because many instructions work with registers directly.

This section describes an alternative method to pass information between the caller and the subroutine it calls. The method is quite general and is used by most high-level programming languages.