Implementing software breakpoints and debugger therefor

Abstract

Program code for a processor is stored in a non-volatile memory (for example, flash memory). An individual data bit stored in a memory cell of the non-volatile memory can be changed from an unprogrammed state to a programmed state using a write cycle. An individual bit stored in the memory cannot, however, be changed from the programmed state back to the unprogrammed state without performing an erase cycle on all the bits of a page of memory cells. The processor has an instruction set that includes a multi-bit breakpoint instruction, all the bits of which are the programmed state. Because all the bits of the breakpoint instruction are the programmed state of the memory, the breakpoint instruction can be written over any other instruction that is stored in the memory without having to perform an erase cycle or erase an entire page of program code.