AVR-Chat

----- Original Message ----- 
From: "Alex De Lara" <alex_de_lara@yahoo.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Wednesday, June 15, 2005 8:20 PM
Subject: [AVR-Chat] Re: This assembly oughta be something silly...


> --- In AVR-Chat@yahoogroups.com, Dave VanHorn <dvanhorn@d...> wrote:
>> >     ldi     ZH,high(Test_str)  ; Load Z register high
>> >     ldi     ZL,low(Test_str)   ; Load Z register low
>> 
>> As a couple of others have pointed out, you need to mult 
>> the string address by two. This is because Z is a BYTE pointer, 
>> pointing to data that is stored as WORDS.
> 
> Ok, I see that.
> 
>> Also, be aware, the data is stored as words by the
>> asembler/compiler, so if you store 
>> "ABC" you'll end up with $41,$42,$43,$00
> 
> That's exactly what I expect if I store strings. (yeah, that
> 0x00 at the end is fine.)
> 
> So, I am looking at the code right now. 
> Just opened the "Memory" window so I could browse all 
> "spaces" (data, program, eeprom, registers, etc)
> My string is actually in the code space, which is fine since 
> right now I just need it to be in someplace.
> 
> What I see is that the instruction
>    ld    r16,Z+
> is not retrieving the byte stored there.
> 
> The address of the begining of the string is physically 
> 0x0016 but when the instruction is executed, some other 
> value comes back to the register (0xFF or 0x00 whenever 
> I use .dseg or leave it out)
> 
> So the question becomes: is there anything else to be set
> so I can tell the Z register to grab the byte located
> in the [code segment]:0x0020 ?
> 
> It seems it is not reading from the code segment, i.e. the
> place where the string is right now.

Try lpm. It puts the byte addressed by the Z register in R0.

Leon

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