Re: [avr-gcc-list] Format of HEX file when program memory addresses exceed 64K

[Graham Davies]

Thanks to everyone who replied to my question:

> What I need to know is what the HEX file is going to look like when my 
> program inevitably grows is size above 64Kbytes.  What mechanism will 
> 'objcopy' use to get above sixteen address bits?

I was hoping to find some actual documentation, but everyone seems to agree 
that the mechanism used is the "Extended Segment Address Record", which is 
record type 02.

David Kelly suggested looking at some source code.  The comments seemed to 
be mostly about what was possible, not what was actually done, but I figured 
things out from the code itself, so thanks very much.

Mark Litwack pointed me to Wikipedia, which was the first place I looked for 
background, but also told me that "avr-objcopy uses record type 02" and 
provided me with the relevant part of a hex file.  I take Mark's point that 
I ought to support both mechanisms (i.e. also the "Extended Linear Address 
Record", which is record type 04), but I'm in one of those situations where 
speed is more important to the customer than thoroughness.  Heck, I've just 
been asked to peer-review someone else's work based entirely on a schematic. 
I will have to guess what it's supposed to do because there isn't a scrap of 
documentation.

Eric Weddington posted a link to the Intel specification and also wrote 
"Look at the "Extended Segment Address Record".

Larry Barello posted a brief description of both mechanism with a 
description of the hex file that matched Mark's clip.

David Brown suggested I try it and see.  That's a fair suggestion, but I'm 
personally resistant to making too many inferences from limited 
observations.  How many different hex files would I have to try before I 
could be sure I'd seen all avr-objcopy's tricks?  I'd rather know what the 
design intent is or, failing that, what the thing is coded to actually do. 
Yes, I'm using an old version of AVR Studio and WinAVR.  But, they do 
everything I need them to and I just don't want to hassle of gaining 
confidence in newer versions right now.

Thanks again, everyone!
Graham.