Setting up stack for subroutines

The code for the above program is:

.include "m328pdef.inc"
start: ;set up the stack
ldi r16, low(RAMEND)
out SPL, r16
ldi r16, high(RAMEND)
out SPH, r16

nop

call below
nop

finish: rjmp finish
below:
ldi r17,$99
ret

The relevant part of the def.inc file the shows what RAMEND is for this processor is:

; ***** CPU REGISTER DEFINITIONS *****************************************
.def XH = r27
.def XL = r26
.def YH = r29
.def YL = r28
.def ZH = r31
.def ZL = r30



; ***** DATA MEMORY DECLARATIONS *****************************************
.equ FLASHEND = 0x3fff ; Note: Word address
.equ IOEND = 0x00ff
.equ SRAM_START = 0x0100
.equ SRAM_SIZE = 2048
.equ RAMEND = 0x08ff
.equ XRAMEND = 0x0000
.equ E2END = 0x03ff
.equ EEPROMEND = 0x03ff
.equ EEADRBITS = 10
#pragma AVRPART MEMORY PROG_FLASH 32768
#pragma AVRPART MEMORY EEPROM 1024
#pragma AVRPART MEMORY INT_SRAM SIZE 2048
#pragma AVRPART MEMORY INT_SRAM START_ADDR 0x100



; ***** BOOTLOADER DECLARATIONS ******************************************
.equ NRWW_START_ADDR = 0x3800
.equ NRWW_STOP_ADDR = 0x3fff
.equ RWW_START_ADDR = 0x0
.equ RWW_STOP_ADDR = 0x37ff
.equ PAGESIZE = 64
.equ FIRSTBOOTSTART = 0x3f00