On compiling. (Was a way off topic subject)

On 6/25/21 3:31 AM, Kelly Fergason via cctalk wrote: This "trick" can be performed on nearly any microprocessor with a stack that keeps return addresses on said stack--and permits a program to push data onto the stack. Certainly x80 and x86 CPUs, where it isn't that uncommon. Interesting status returns can be implemented by adjusting the return address on the stack in sort of a "reverse" computed goto; e.g. sub_entry:.... add [stack top], status*jump instruction size return ...calling code... call sub_entry jmp status_0 jmp status_1 jmp status_2 ..etc. Which saves the caller from having to perform multiple compares (or a computed GOTO) on the status return. On lower PIC microcontrollers, there is no way for a program to access code space (i.e. Harvard architecture). Static lookup tables represent a concept requiring some thought. Low PIC code memory uses 13 bit words, while data memory uses 8. Fortunately, there is an opcode, RETLW, that is "return from subroutine with 8 bit value in the W register". So one codes a table of RETLW xx instructions and performs an indexed call into it. --Chuck