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My program works wrong because of c compiler's optimization. If I use "volatile" to declare some varibles and functions, the optimization will be affetced, and perhaps the program works well, but if I changed the program, I would have to add "volatile" to other varibles or functions. I have to try many times to make compiler compile my program "correctly" after change the program. Is there a way to remove optimization completely? I use #pragma SAVE #pragma OPTIMIZE(0) my_func1() { ...; } #pragma RESTORE but I know optimize level 0 doesn't mean no optimization, and my program can't be compiled correctly even at optimize level 0, if without "volatile" to most varibles and functions. I only use P0, P1 and P2, to read and write some IO lines. Compiler is keil c51 v6.12
Yes, interrupt affects the program. Here is the example: /* global varibals shared between uart_listener() and main() */ volatile uchar uart_input_flag; volatile uchar uart_input_grp; volatile uchar uart_input_smc; void uart_listener(void) interrupt 4 { static uchar stat = 0; uchar c; if (!RI) return; c = SBUF; RI = 0; if (stat == 0) { if (c == KVM_CMD_DATA) stat = 1; } else if (stat == 1) { uart_input_grp = c; stat = 2; } else if (stat == 2) { uart_input_smc = c; uart_input_flag = 1; stat = 0; } } If I remove uart_listener(), my program works well; or if I add "volatile" to local varibal "stat" and "c" my program works well too. Perhaps it's not a optimize problem? /* global varibals shared between uart_listener() and main() */ volatile uchar uart_input_flag; volatile uchar uart_input_grp; volatile uchar uart_input_smc; void uart_listener(void) interrupt 4 { static volatile uchar stat = 0; volatile uchar c; if (!RI) return; c = SBUF; RI = 0; if (stat == 0) { if (c == KVM_CMD_DATA) stat = 1; } else if (stat == 1) { uart_input_grp = c; stat = 2; } else if (stat == 2) { uart_input_smc = c; uart_input_flag = 1; stat = 0; } } ============ Another problem, functions as static volatile void test1() { ....; } static volatile char test2() { ....; } can be compiled well. I'm not sure what's the meaning of a volatile function, or does it means nothing?
I have found the real reason is the broken hardware! The AT89C52 I was using is damaged, and caused wrong IO. After using new AT89S52 instead of the old chip, everything OK. There is no bussiness about optimize and volatile varibles, it's a hardware fault. Thanks.