AVR-Chat

As far as I can see, I am initializing the stack point to RAMEND, but 
when i simulate this code, i am getting an uninitialized stack error 
when the rcall instrcution is hit.  Why for?


.include "tn25def.inc"

; Define here the variables
;
.def  temp  =r16

; Define here Reset and interrupt vectors, if any
;
RESET:
   rjmp START
   reti      ; Addr $01
   reti      ; Addr $02
   reti      ; Addr $03
   reti      ; Addr $04
   reti      ; Addr $05
   reti      ; Addr $06        Use 'rjmp myVector'
   reti      ; Addr $07        to define a interrupt vector
   reti      ; Addr $08
   reti      ; Addr $09
   reti      ; Addr $0A
   reti      ; Addr $0B        This is just an example
   reti      ; Addr $0C        Not all MCUs have the same
   reti      ; Addr $0D        number of interrupt vectors
   reti      ; Addr $0E
   reti      ; Addr $0F
   reti      ; Addr $10


; Program starts here after Reset
;
START:
 
;    this table povides the data for the intensity curve needed for
;    xxxxxxxxxxxxxxx.  the data represent the value sin^3 * 255 for
;    each angle from 0 through 90  at .9 degree increments

    .eseg

TABLE:
    .db    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 2, 3, 3, 4, 5, 6, 6
    .db    8, 9, 10, 11, 13, 14, 16, 18, 20, 22, 24, 26, 29, 31, 34, 36
    .db    39, 44, 48, 52, 55, 59, 62, 66, 70, 74, 78, 82, 86, 90, 94, 99
    .db    103, 108, 112, 117, 121, 126, 130, 135, 140, 144, 149, 153
    .db    158, 163, 167, 172, 176, 180, 185, 189, 193, 197, 201, 205
    .db    209, 212, 216, 219, 223, 226, 229, 232, 234, 237, 239, 242
    .db    344, 346, 247, 249, 250, 252, 253, 254, 255, 255, 255
     
;
     .cseg


BEGIN:

    ldi    r30,    RAMEND                    ; initialize stack pointer
    out    SPL,    r30
   

    ldi    r31,    0x00                    ; set up EEPROM high byte address
    out EEARH,    r31                        ; store in register

    ldi    r31,    0x00                    ; set up upper WGM bytes
    out    WGM01,    r31                        ; and once again
    ldi    r31,    0x03                    ; set upo to set waveform 
configuration
    out    WGM00,    r31                        ; output to appropriate 
control register

;
;    set up timer delay for ~~.01 second
;
;    counter clock will be prescaled by 1024 to make the .01 second 
count easier
;

    ldi    r31,    0x38                    ;  load low byte of delay count
    out    TCNT0,    r31                        ; output to counter/timer 0-

    ldi    r31,    0xe5                    ; load the control value for 
TCCR1
                                        ; CTC1 set, PWMa set, COM1A set to
                                        ; toggle on match, timer clock set
                                        ; for system clock divided by 256

    out    TCCR1,    r31                    `    ; store in register

    ldi    r31,    0x01                    ; load value for TCCR01A
    out    TCCR0A,    r31                    ; and strope to TCCR01A
    ldi    r31,    0x04                    ; load value for TTCCR01B
    out    TCCR0B,    r31                    ; output to TCCR01B

    ldi    r31,        0x00                ; load compre output macthj value
    out    OCR0A,        r31                    ; stroe in output 
compare register 0A


;
;    this code sets the default initial table adress at -1.  It will 
automatically
;    increment on the first access, to 0
;

    ldi    r16,    0xff                    ; first addresss - 1 in 
EEPROM table data
    ldi r17,    0x00                    ; direction control byte, 0 = up

    rcall    TABLEDATA

    rjmp    DONE                        ; all done, leave
;
;    this subroutine counts up and down through the data table in the EEPROM
;    data, reading all 100 data values, from bottom to top, then top to 
bottom
;    one at a time
;

NEXT:

    ldi    r30,    0x00                    ; compare value
    cp    r17,    r30                        ; check direction bit for value
    brne    UP                            ; it's set for an up count
   
    ldi    r30,    0x00                    ; compare value
    dec    r16                                ; count the table pointer 
down one
    cp    r16,    r30                        ; at the bottom yet?
    ldi    r17,    0xff                    ; set direction flag to count up
    RJMP    QUIT0                        ; all done, depart

UP:
    ldi    r30,    0x63                    ; compare value
    inc    r16                                ; increment table pointer
    cp    r16,     r30                        ; 99 decimal, end of table
    breq    FIXIT0                        ; deal with table overflow
    rjmp    QUIT0                        ; all done, depart


FIXIT0:

    ldi    r17,    0x00                    ; reset direction flag for 
down count
           
QUIT0:

    ret                                    ; return from subrouttine 
call   

;
;    read a value from the EEPROM table
;

TABLEDATA:

    rcall    NEXT                        ; go grab next tabel address
    out    EEARL,     r16                    ; move table value address 
to EEPROM
                                        ; address register low byte
                                       
    in    r0,        EEDR                    ; read data from EEPROM 
data register
   
    ret                                    ; all done, go home   



DONE:
    rjmp DONE

    .exit