| 摘要 |
PURPOSE:To restore a microprocessor to normal operation by detecting the malfunction to cause the initializing operation by a reset synthesizing circuit if a vertical address is not changed three horizontal periods or more. CONSTITUTION:The waveform of a horizontal synchronizing pulse input terminal 1, the a/8 waveform of a frequency divider 29, and input waveforms of FFs 20, 21, and 22 are denoted as (a), (b), (c), (d), and (e) respectively. If the malfunction occurs in the fifth period of the waveform (a), the waveform (a) is in a low level in following periods, and waveforms (c), (d), and (e) go to the low level at the time of the seventh period. Therefore, an output (f) of an AND gate 27 goes to a high level through inverters 23-25 and an output (g) of an OR gate 28, namely, the output of a malfunction detecting circuit 32 goes to the high level. As the result, an output (h) of a NAND gate 30 goes to the low level in the tenth period of the waveform (a), and a supply voltage rise detecting signal terminal 11 is in the normal high level, and an output (i) of an AND gate 31, namely, an output (i) of a reset synthesizing circuit 33 is in the low level only in the tenth period of the waveform (a). Consequently, each circuit is initialized and is restored to the normal operation. |
