AVR-Chat

Changed the code. Using GPIOR0,0 as a flag and a test loop on the register 
when the interrupt completes. Works fine.
Found what might be another little problem though. The GPIOR0, 1 and 2 
registers are supposed to work with the sbi, cbi, sbis and sbic 
instructions. GPIOR0 works fine, the others give me an "operand out of 
range" error when I build the code.
Thanks
Dennis
----- Original Message ----- 
From: "John Samperi" <samperi@ampertronics.com.au>
To: <AVR-Chat@yahoogroups.com>
Sent: Tuesday, August 23, 2005 5:01 PM
Subject: Re: [AVR-Chat] Re: mega 168


> At 12:12 AM 24/08/2005, you wrote:
>>Not that I disagree with you, however, look at the RETI for th 8051. Also,
>>check out the RET and RETI instruction explanantion is the instruction set
>>manual. Both of the latter use the same stack operation implying they
>>function the same. RET returns to the instruction following the CALL, RETI
>>does not.
>
> Well there is an easy way to find out, translate your code to 8051
> code and run it in a simulator and see if it works differently to
> the AVR and let us know. I have been working with microprocessors for
> some 25 years and with at least a dozen different families/architectures
> and I haven't seen a processor behave like you expect.
>
> You can use your loop as long as you understand that
>
> loop:
>         rjmp loop
>
> will ALWAYS and regardless of what happens anywhere else jumps
> to itself so that the next instruction to be executed is rjmp loop
>
> If on the other hand you put some code in your loop that tests
> something for true or false and that something can be changed
> by an interrupt then it will work well.
> Let's say you enter your loop with r16=0 and your interrupt
> routine changes it to 1 then you could do the following:
>
> loop:
>         tst r16         ;Check if r16 is still 0
>         brne exit_loop  ;If no longer 0 then exit the loop
>         rjmp loop       ;otherwise keep on waiting
> exit_loop:
>         more instructions
>
> In your code you seem to test portd for some pattern
> put this test within your loop and it will work but
> by having an interrupt just happening will not exit
> a loop.
>
>
> Regards
>
> John Samperi
>
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