| 摘要 |
PURPOSE:To attain the accurate detection of an overflow by providing a comparator to detect that the stack pointer of a CPU or the contents of a program counter exceed a normal limit level. CONSTITUTION:A stack pointer limit value detecting circuit 21 is set at a level equivalent to an address Y, i.e., the deepest memory address of a stack area 12C. Thus a comparator 20 activates a fault signal 20a when the stack pointer of a CPU 10 is equal to the level equivalent to the address Y and at the same time gives an indication to the CPU 10 to stop its processing. Thus it is possible to detect that the stack pointer of the CPU 10 is set at a level equivalent to the deepest memory address of the area 12C. Then the overflow of the area 12C can be monitored and the software runaway can also be detected. |
