[fasm-help] nice macro when no ram!

[Anthony <an...@do...>]

Hi,

Anyone writing a bios using fasm may find this macro helpful, it
allowed me to get rid of a lot of wasteful repetitive code.  The
problem normally being that until you setup a stack, you cannot use
subroutines.  And until you set up dram, you can't set up a stack!

With the macro below, you just use "spcall routinename", you must
however make sure that the you copy cs to ss at the start of your
bios.  Calls can only be one level deep.

; this macro does a call when there is no stack
  macro   spcall addr
  {
          local   deststack,destaddr
          mov     sp,((deststack)and $ffff)  ; point stack to data after jmp instruction
          jmp     addr                       ; do the routine
deststack: dw      ((destaddr)and $ffff)     ; when a retn is executed...
destaddr:                                    ; ... it will return to this address - pulled off the stack!
  }



-Anthony                            mailto:an...@do...

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