a conflict variable

[stefsun]

A variable can be read, and also can write, if there is a conflict, one is reading the variable, and the other is writing the variable. In the case，error will be there. How to solve the problem ?
I know that VC can use the mutex or Critical Section the problem, but in CCS, I do not know how to solve the problem.

for example

[RLScott]

There is nothing like a mutex or Critical Region provided by the CCS compiler. But you can provide your own if you need to. Normally you don't need these formal objects.

In your example,if adc_val is a single byte, then there is no conflict. Whenever INT_TBE gets control, it will use the most recent value of adc_val that was written by the main program. But if the shared variable is two or more bytes, then you may have to take some precautions. There are several ways to resolve the conflict, depending on the needs of your application:

1. Disable the interrupt in main() before writing the variable, and then re-enable the interrupt afterwards.

2. Set a flag variable in main before writing the variable and clear that flag afterwards. Then design the interrupt code so that is does not use the shared variable if the flag is set. What it does do when the flag is set is up to you. Perhaps it is OK to do nothing. Or else it could use an old value saved from before.

3. If the interrupt is periodic, then wait in main until just after the interrupt hits before writing the shared variable. Then the interrupt will not hit during the writing of the variable.

And there may be other solutions.

Robert Scott
Real-Time Specialties

[Matro]

[stefsun]

thanks Matro and Robert Scott