Do you have a question? Post it now! No Registration Necessary
- Meindert Sprang
January 9, 2004, 2:47 pm

Hi,
I found that when I compile a certain project in Imagecraft AVR for the
90S8515 or for the mega8515, the relative code sizes are 92% and 84%
respectively. Is this the result of new instructions I am unaware of or can
the Imagecraft compiler produce tighter code because some silicon bugs have
been resolved on the mega8515?
Meindert
I found that when I compile a certain project in Imagecraft AVR for the
90S8515 or for the mega8515, the relative code sizes are 92% and 84%
respectively. Is this the result of new instructions I am unaware of or can
the Imagecraft compiler produce tighter code because some silicon bugs have
been resolved on the mega8515?
Meindert

Re: Code difference AVR 90S8515 vs. ATmega8515

can
have
There are some new instructions, and some variations on existing ones.
Differences include movw instructions for moving two registers at once,
different addressing modes for the lpm instruction, and a hardware
multiplier which makes multiplication code (including array access) much
smaller.

Re: Code difference AVR 90S8515 vs. ATmega8515

Signature bytes do not really protect against the problem, which is
accidental ship (by a user of both devices) of Mega8515 code into a
90S8515 device.
Meindert was sharp enough to spot that the change of target gave
different code sizes - the average AVR user is rather more likely to
'find out the hard way' - tho you could argue that since clearly
(90S <> Mega) then it is user beware....
It would probably help if
AVR085: Replacing AT90S8515 by ATmega8515
mentioned that opcode changes mean a Mega8515 build may no longer
be backward compatible on any existing 8515 products.
- ie as a mid-run production change, there are risks.
-jg
Site Timeline
- » Atmel STK500 beginner Flash mem verification problem
- — Next thread in » Embedded Programming
-
- » Need FAT32 Source Code
- — Previous thread in » Embedded Programming
-
- » Ceramic capacitor failure
- — Newest thread in » Embedded Programming
-
- » stampante termica gebe flash 4378
- — The site's Newest Thread. Posted in » Electronics Hobby (Italian)
-
- » Ceramic capacitor failure
- — The site's Last Updated Thread. Posted in » Embedded Programming
-