I have some doubt about "push" and "pop" depth.

my program was supposed to get a string in XDATA and show it in a display, but the display routines also used DPTR, so I did something like:

mov dptr, #stringpush dpl
push dph
call display_main_routine
push dpl
push dph
call display_subroutine
push dpl
push dph
mov dptr, #foo
;execute suboroutine
pop dpl
pop dph
pop dpl
pop dph
pop dpl
pop dph

it wasn't working, looking the code under RIDE51 simulator I observed that the last pop's weren't returning the value that I stored.

I solved that problem storing the value of DPTR in the XDATA area, but what I really want to know is if there is some "depth" when push'ing a register (a depth of two push'es, from my observations)
I couldn't find a limit to use with push in my books, but most of the examples needed only one, at most two push'es, so I'm asking for some clarification.

TIA

orlando