| 摘要 |
PURPOSE:To detect the runaway of a microprocessor precisely by detecting the runway on the basis of a signal indicating access to a program area or another area and a status signal outputted during instruction fetching. CONSTITUTION:When the microprocessor 1 is operating normally, a program area in a memory is accessed during instruction fetching, but an area other than the program area is accessed in a time other than the instruction fetching. A signal A1 is in the H level when a status signal M1 is in the L level, but is in the L level when the status signal M1 is in the H level, so that no L level signal is outputted from an AND gate 16. If the microprocessor runs away, the signal A1 is turned to the L level when the status signal M1 is in the L level during the instruction fetching, so that the output signal of the AND gate 16 is turned to the L level and a reset pulse generating circuit 12 supplies an L level signal to a reset terminal of the microprocessor 11 to reset the microprocessor 11. |
