My timer code is failing when IAR is configured to do max optimization
I have used timer A in MSP430 with high compiler optimization, but found that my timer code is failing when high compiler optimization used. When none optimization is used code works fine.
This code is used to achieve 1 ms timer tick. timeOutCNT is increamented in interrupt.
Following is the code
//Disable interrupt and clear CCR0
TIMER_A_TACTL = TIMER_A_TASSEL | // set the clock source as SMCLK
TIMER_A_ID | // set the divider to 8
TACLR | // clear the timer
MC_1; // continuous mode
TIMER_A_TACTL &= ~TIMER_A_TAIE; // timer interrupt disabled
TIMER_A_TACTL &= 0; // timer interrupt flag disabled
CCTL0 = CCIE; // CCR0 interrupt enabled
CCR0 = 500;
TIMER_A_TACTL &= TIMER_A_TAIE; //enable timer interrupt
TIMER_A_TACTL &= TIMER_A_TAIFG; //enable timer interrupt
TACTL = TIMER_A_TASSEL + MC_1 + ID_3; // SMCLK, upmode
timeOutCNT = 0;
//timeOutCNT is increased in timer interrupt
while(timeOutC开发者_如何学运维NT <= 1); //delay of 1 milisecond
TIMER_A_TACTL = TIMER_A_TASSEL | // set the clock source as SMCLK
TIMER_A_ID | // set the divider to 8
TACLR | // clear the timer
MC_1; // continuous mode
TIMER_A_TACTL &= ~TIMER_A_TAIE; // timer interrupt disabled
TIMER_A_TACTL &= 0x00; // timer interrupt flag disabled
Can anybody help me here to resolve this issue? Is there any other way we can use timer A so it works fine in optimization modes? Or do I have used is wrongly to achieve 1 ms interrupt?
Are TIMER_A_TACTL
and others volatile
? If not, the compiler may reorder or combine reads and writes, under the assumption that these have no side effects.
You should be able to solve by either introducing barriers at appropriate positions, or by declaring these variables as volatile
Have a look at the list file output to see whether the assembler output contains output for the line
while(timeOutCNT <= 1);
If you are using the kickstart version of the compiler then the list file will not contain the assembler listing and you should load the code into C-Spy and look at the disassembler listing there.
I suspect that Hasturkun is on the right lines in that you have probably not declared timeOutCNT
as volatile
. If you forget this then the optimiser will assume that the while statement will reduce to
while (1) ;
I can't comment specifically on your timer code, but I saw a similar problem in general. When high levels of optimization were used, code would break in various places in seemingly unrelated ways. We ultimately chalked it up to compiler bugs then disabled optimization completely.
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