For some good docs written by a friend of mine, check out the avr
material on this page:
http://eecs.oregonstate.edu/education/classes/ece375/index.html

It should get you up and running quickly.

-Shawn



Randy Ott wrote:

> Roy,
>
> Take a look at a program I wrote as a learning exercise that does something
> simular to what you are trying to do.  It is a simulation of the old "magic
> 8 ball" that reads message strings from flash and displays them on an LCD.
> The best example is one that outputs to the UART and is named 8BALLSIO.ASM
> and is located at www.qsl.net/k5hj/avr along with a bunch of other small
> programs I did in order to learn about the AVR.  Most are written for the
> 2313 but should apply to the MEGA parts as well.
>
> Randy Ott
>
> On Sat, 12 Jun 2004 09:07:25 +1200, Hopkins wrote
>
>>Thanks again David -
>>
>>just one point I do not understand and that is how do you know the
>>Table_Offset value or how do you know just were the table is located
>>in memory?
>>
>>*************************************************
>>Roy Hopkins   :-)
>>
>>Tauranga
>>New Zealand
>>*************************************************
>>
>>>>How do you program a lookup table in an AVR (ATMega 8) using assembler
>>
>>code?
>>
>>>Assuming two regs named TEMP, TEMP2, and a ram var called Table_Offset
>>
>>with the pointer to the position in the table:
>>
>>>Get_Table_Byte:
>>>        ldi     TEMP,0                  ;For the 16 bit add to follow
>>>        lds     TEMP2,Table_Offset      ;Get the offset
>>>        ldi     ZL,low(Table*2)         ;Point at the table
>>>        ldi     ZH,high(Table*2)        ;
>>>        add     ZL,TEMP2                ;Add the offset as a 16 bit op
>>>        adc     ZH,TEMP                 ;so the table can be anywhere.
>>>        lpm     ;Defaults to R0, some AVRs can put it in other registers.
>>>
>>>        ret     ;Byte (Table offset) of TABLE is now in R0
>>>
>>>For reading multiple bytes, continue with
>>>
>>>adiw    ZL,1
>>>lpm
>>>
>>>and so on.
>>>
>>>Data is stored in WORDS in the AVR rom, but recalled in BYTES.
>>>Also, the assembler will append an extra null to the end of a .db that is
>>
>>an odd number of bytes long.
>>
>>>TABLE: .db 0x45,0x46,0x47
>>>
>>>Ends up in rom as 45,46,47,00 << Extra null added by assembler.
>>>
>>>A table that ends in a null, like:
>>>
>>>TABLE: .db 0x45,0x46,0x43,0x47,0x00
>>>
>>>ends up looking like this: 45,46,43,47,00,00
>>>
>>
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