uVision3 Bug?

Thanks for your answers, but i still have the problem.
I tried to shorten the code as much as possible.
If you replace the function call "get_taste()" with the code within the get_taste-function-code then it works ok. But i don't understand why. There should be no difference.
Christian Tauschek

unsigned char tp[2];
unsigned char n, r1;

void timer1_isr(void) interrupt 3 using 1 {
     TL1 = 0xef;
     TH1 = 0xd8;

     // if i replace this call "get_taste()" with
     // the get_taste-code below, then it works ok
     get_taste();
}

void get_taste(void) {
     tp[0x00] = 0x0a;
     tp[0x01] = 0x0b;
     n = 0x01;
     tp[n] = tp[n - 1]; // there is the MISTAKE

     // now i expect the value 0x0a in r1, but r1
     // has the value 0x00
     r1 = tp[n];
}

Thanks for your answers, but i still have the problem.
I tried to shorten the code as much as possible.
If you replace the function call "get_taste()" with the code within the get_taste-function-code then it works ok. But i don't understand why. There should be no difference.
Christian Tauschek

unsigned char tp[2];
unsigned char n, r1;

void timer1_isr(void) interrupt 3 using 1 {
     TL1 = 0xef;
     TH1 = 0xd8;

     // if i replace this call "get_taste()" with
     // the get_taste-code below, then it works ok
     get_taste();
}

void get_taste(void) {
     tp[0x00] = 0x0a;
     tp[0x01] = 0x0b;
     n = 0x01;
     tp[n] = tp[n - 1]; // there is the MISTAKE

     // now i expect the value 0x0a in r1, but r1
     // has the value 0x00
     r1 = tp[n];
}

Note the use of "using 1" which selects a specific register bank.

But how would get_taste() know that you call it from an ISR that is "using 1"?

When you mix code using different register banks, then you can get these effects.

Memory location 6 is always at the same place, but the definition of R6 will change depending on the currently used register set (the "using" part).

void get_taste(void) {
     tp[0x00] = 0x0a;
     tp[0x01] = 0x0b;
     n = 0x01;
     tp[n] = tp[n - 1]; // there is the MISTAKE

No. That is only where the mistake caused elsewhere finally bites.

There is a pair of places where the mistake is: you call a function from an ISR qualified "using 1", but the called function itself is not qualified "using 1". That combination is a monstrously big NO-NO.

Hello all,
thanks for answers. Now, without "using 1", it works fine.
I caused the mistake.

Christian Tauschek

However, using significantly reduces the overhead in your ISR - so you should really know how to use it properly (even if it isn't needed in this particular case)

See http://www.keil.com/support/man/docs/c51/c51_le_regbankaccess.htm for details.

Also: http://www.keil.com/support/man/docs/c51/c51_le_regbankspec.htm and the linked knowledgebase articles.