Jan Waclawek wrote: >> Why would the compiler respect assembler any more than my C calls >> > > > Because the compiler knows nothing on assembly language. It simply passes it > as a string to the assembler: it does not attempt to parse it (except for the > escape sequences), so it has no chance to modify the order of anything. > > On the other hand, a compiler is free to do whatever it wants to do with > statements you pass to it: it can reorder and insert voids wherever and > whenever it wants. This is the very principle of high level languages: you > give up part of control in exchange of increase in convenience. If you want > to re-gain control for whatever reason, the best thing to do is to revert to > assembler. > > As I said, you can make this a standalone assembler source, if you feel more > comfortable with it, and the link it together. The same thing can be done > with variables, see attachment - this avoids the need to put all variables > into a single struct (to ensure their fixed order); but I don't say this is > the best way to do with variables. > > JW Jan,
OK, sounds good, If GCC really will leave my assembler alone then that would be the best way to go. I am no longer so worried about the variables, although they were my original concern - I have written helper functions which make them transparent to the 'other side' and I think this is better practice. All I need now is the jump table... David, >> While it's good practice to design your protocol to handle errors, you shouldn't be seeing ANY errors wether or not the port is USB. I'd look to solving >> that problem. Are you sure that your baud rate is correct? Yes, quite sure. This is a known (to me) issue with FDDI USB to serial chips. If use a level converter and 'proper' RS-232 with the same setup I never ever get an error. The receive side uses a circular buffer with high & low water marks and therefore can do 'proper' handshaking. It's just that i cannot rely on a modern (cheap) PC having a serial bus. The errors are only very occasionally, hardly an issue with my data volumes. They would become a problem if I started transferring large chunks. Tracking the FDDI down will have to wait. Many thanks for all your comments, they are really a big help, Robert _______________________________________________ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
