| Author |
Message |
|
|
 Posted: Jan 21, 2012 - 07:00 AM |
|
Joined: Oct 23, 2011
Posts: 2
|
|
I am a starter and I want to write a small AVR assembler program. Add 5 numbers defined in the memory and stored into r0 finally. My code can be assembled successfully. But there is a warning about "warning: .cseg .db misalignment - padding zero byte".
The problem is, r0 and r1 keep being 0 all the time when debugging step by step. I don't know why. Please help me and thanks a lot!
My code:
Code:
.NOLIST
.INCLUDE "m328Pdef.inc"
.LIST
; Code starts here
;Data starts here(On this processor this is always 0x0100)
.dseg
data: .BYTE 5 ;Space for 5 bytes
sum: .BYTE 1 ;Space for result
.cseg
jmp main;
main:
var: .db 0x09,0x02,0x03,0x04,0x05
LDI r16,LOW(RAMEND) ;Initiate Stackpointer
OUT SPL,r16
LDI r16,HIGH(RAMEND)
OUT SPH,r16
clr r0
ldi r16,5
ldi XH,high(var)
ldi XL,low(var)
loop:
ld r1,X+
add r0,r1
dec r16
brne loop
st X+,r0
sleep
|
|
|
| |
|
|
|
|
|
|
Posted: Jan 21, 2012 - 07:24 AM |
|
Joined: Oct 23, 2011
Posts: 2
|
|
| By the way, I don't understand the so called "byte address" in the program segment. Anyone can help me understand this? |
|
|
| |
|
|
|
|
|
|
Posted: Jan 21, 2012 - 07:31 AM |
|
Joined: Mar 28, 2001
Posts: 20387
Location: Sydney, Australia (Gum trees, Koalas and Kangaroos, No Edelweiss)
|
|
|
Quote:
But there is a warning about "warning: .cseg .db misalignment - padding zero byte".
The assembler is helping you out by putting a zero in the last loacation to keep the data on even boundaries. Remember that data is kept in 16 bit locations therefore 2 bytes per address is used.
Code:
jmp main;
main:
var: .db 0x09,0x02,0x03,0x04,0x05
EXTREMELY BAD idea. The first thing the processor will do is trying to use your data as instructions with unkown results. Move you data at the end of the program after some terminating loop.
Code:
.
.
st X+,r0
sleep
loop:
rjmp loop
var: .db 0x09,0x02,0x03,0x04,0x05
And finally you CANNOT get data from the Flash as you are trying to do. Read up on the LPM instruction. |
_________________
John Samperi
Ampertronics Pty. Ltd.
www.ampertronics.com.au
* Electronic Design * Custom Products * Contract Assembly
|
| |
|
|
|
|
|
|
Posted: Jan 21, 2012 - 08:14 AM |
|
Joined: Mar 27, 2002
Posts: 18576
Location: Lund, Sweden
|
|
Sometimes the search function here at AVRfreaks fails, but it does an excellent job for e.g. "misalignment - padding zero byte". Don't forget to tick "Search for all words". It will give you excellent prior explanations for this message, e.g.: http://www.avrfreaks.net/index.php?name ... +zero+byte .
Also note that in that thread there is a link to a prior thread with more discussion.
I'm sure there are other valuable reads on this subject if you go through more of the search results. |
|
|
| |
|
|
|
|
|
|
Posted: Jan 22, 2012 - 04:55 AM |
|
Joined: Nov 17, 2004
Posts: 13847
Location: Vancouver, BC
|
|
|
Quote:
And finally you CANNOT get data from the Flash as you are trying to do.
To be more specific, you are putting "var" into flash, but trying to read it from SRAM. |
_________________
Regards,
Steve A.
The Board helps those that help themselves.
|
| |
|
|
|
|
|
|
Posted: Jan 22, 2012 - 10:38 AM |
|
Joined: Jul 18, 2005
Posts: 62341
Location: (using avr-gcc in) Finchingfield, Essex, England
|
|
|
Quote:
To be more specific, you are putting "var" into flash, but trying to read it from SRAM.
To be even more specific - look up the LPM opcode in your manual. |
_________________
|
| |
|
|
|
|
|
FAQ
Search
Register
Log in to check your private messages
Log in
Maximize
RSS
