I¡¦m a Hong Kong student and I¡¦m doing my final year project. It¡¦s a security and automation system. A 4*4 keypad and a LCD are connected to the 89c52 chip. When I run the program, it¡¦s no problem initially, however, it¡¦s hanged after several minutes. My friend told me that it¡¦s because there is not enough place for the stack, so I start the stack pointer at #3ch, it¡¦s already the lowest position because the lower memory are use to store some parameter like time and password. But the problem can¡¦t be solved. It¡¦s hanged again.
Also, I have connected a 555 timer to the external interrupt 0 to generate a 1Hz clock to the 89C52 chip to act as a clock. From the connected LCD, the time can be showed.
Sometimes, when I changed the stack pointer, the interrupt didn¡¦t work. I have tried many positions for the stack, but the about two problems still occur. Either one of them occurs. Is the problem come from the stack? Or other reasons? Where should I place the stack? My program is about 16 pages long and contains many lcall, ljmp command, will it have problems?