I was working on an application using UART FIFO receive interrupts with CCS 5.1 and StarterWare_02_00_00_04 . Once I had the problem that the code ran to the Abort/Undefined-Instruction Handler. After doing some debugging, I found that a parameter passed to a function call was not the correct value in the UART ISR. By stepping through the assembly codes of ISR, one line of code was “MOV R0, R6”. R6 held the correct value I intended to pass to the function. But once executing this line of code, R0 remains its original value, not the value in R6. Later R0’s value was passed to the function and caused wrong behavior in the function.
I have following questions:
Any help is greatly appreciated.
Its quite strange that you are not able to see the R0 value in R6. I have never faced this problem with CCS.
Yanli:Is there any “protection mode” that prevents the changes of register values?
No. There is no protection enabled which can result in this kind of behavior.
Yanli:While stepping through the assembly codes, can I trust the register values shown by CCS between executing every instructions?
Normally, we can. Hope you are using the version of CCS we suggest for StarterWare, v220.127.116.11, http://processors.wiki.ti.com/index.php/Download_CCS and debugging on Beaglebone.
Yanli:By changing one local variable in the ISR to “volatile” (which is unrelated to the problematic function call) and compiling the project again, the compiler re-arranged the variables and the above line of code was changed to “MOV R0, R7”. This time R0 changed to value of R7 and the function got the right parameter. So why “MOV R0, R7” worked but “MOV R0, R6” didn’t
It is strange :( . So, even after reaching the function entry, after executing BL instruction, R0, the first parameter for the function is wrong ?
And, after you declared the variable volatile, did your function(which is called from the ISR) work ?
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.