I am attempting to debug a pair of CAN nodes. I have included a link to an AVRstudio screen shot showing R24 with a 0x57 value writing to SRAM special function I/O register address 0xEF (CANCDMOB) with a STS instruction and having CANCDMOB show a value of 0x97, not 0x57.
The screen shot is in disassembly view just after a F11 single step. It really shouldn't matter, but this is WinAVR 20100110. This debugging failure is produced with a simple run to cursor, then F11 single steps to get to the bad STS operation.
This is quite simply supposed to be impossible. There is no AT90CAN128 data sheet errata for this. Has anyone ever seen this behavior?
I can make the source code available for reproducing the failure, but you will need two connected operational AT90CAN128 CAN nodes with JTAGICE mkII hardware to check this problem. If anyone has the required hardware and is willing to help, please let me know (reply to this thread) and I'll get you the source code.
Link to AVRstudio screen shot: