AVR-Chat

I don't know but it looks to me like you're jumping to the table at the 
start of your program, not to BEGIN.  I think your first code line after 
RESET should be "rjmp BEGIN".

Your program is going to try to execute your table as code, and who knows 
where you will end up?

Zack

On Tue, 2 Jan 2007, Thomas Keller wrote:

> 
> 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
>    
>