Hi,
first of all - do not panic! (=
suggestion:
- use registers and on-chip XRAM for passing parameters between functions.
- do not call-call-call functions in deeeeep nesting. Instead it, create task dispatcher in main loop and a variable-descriptor which will indicate where your logical sequence is.
- if you still need with many nested levels - do not use CALLs. Use JUMP and a variable where place return address in. In this case use JUMP (varibale) instead RET for return from subroutines.
Now, do you use C or ASM?
In C: it depends on compilers, for example, Keil has options to use reentrant stack pointer (for LARGE model it may be even 64kB). Read manual.
In ASM: yes, it is possible to flush stack into XRAM, reinitialize SP with new value, execute some functions and move stack back from XRAM. But be careful - it requires alot of attention - disable interrupts due moving, do not return to functions of previous levels before restore old stack etc.
Good days!