METHOD AND APPARATUS FOR FAST MICROCONTROLLER CONTEXT SWITCHING

摘要

A microcontroller apparatus and method providing a program status word (PSW) including system status bits that can be stored and loaded along with a program counter (PC) during a context switch operation, such as when processing an interrupt or launching an application. The status bits indicate mode (system or user), designate which registers banks are used as general purpose registers and indicate the interrupt priority of the program being executed. By loading a PSW relevant to the task to be executed into the program status word register and loading a PC providing an entry point of the task into a fetch unit, the microcontroller immediately begins task execution. An interrupt vector of the microcontroller system includes the PSW and PC of the particular interrupt allowing immediate processing of the interrupt reducing system overhead tasks. A return from the task, such as via a return-from-interrupt, restores the PSW of the prior task as well as the PC from a system stack, thereby rapidly switching the context back to the prior task. By loading an application specific PSW and PC (and appropriate general purpose registers and special function registers is necessary), and then initiating a return-from-interrupt the microcontroller allows rapid initial task launching.