IP2022 User’s Manual—Instruction Set Architecture www.ubicom.com 69 The following code example uses indirect-with-offset addressing. When bit 7 of the “fr” field is set, the SPH/SPL register (i.e. the
stack pointer) is selected as the pointer register. The upper four
bits of the SPH register are not used. Figure 3-6 shows indirect-
with-offset addressing using the SPH/SPL register as the pointer
register. In addition to this indirect-with-offset addressing mode,
there  are  also  push  and  pop  instructions  which  automatically
increment and decrement the SPH/SPL register while performing
a  data  transfer  between  the  top  of  stack  and  a  data  memory
location specified by the “fr” field. Stacks grow down from higher
addresses to lower addresses. This stack addressing mechanism
is independent from the hardware stack used for subroutine call
and return. When   a  pop  instruction  is  used  with   the   indirect-with-offset
addressing mode, the address calculation for the “fr” operand is
made   using   the   value   in   the   SPH/SPL   register   before   the
automatic  increment,  even  though  the  stack  operand  itself  is
addressed using the value after the automatic increment. MyStuff=   0x0385 ;define address MyStuff loadh MyStuff ;load the high byte of the
;DPH/DPL register with 0x03 loadl MyStuff ;load the low byte of the
;DPH/DPL register with 0x85 mov w,8(dp) ;load W with the contents of
;the memory location at
;address 0x38D
;(i.e. 0x385 + 0x008)