Title:
CONTROL CIRCUIT FOR PROGRAMMABLE CONTROLLER
Document Type and Number:
Japanese Patent JPS6389901
Kind Code:
A
Abstract:
PURPOSE:To continue or stop an operation even at the time of abnormality by providing a logic circuit that detects abnormality of a programmable controller by an external equipment and outputs a signal to operate the plant/process to safety side. CONSTITUTION:A monitoring device 5 monitors output signals of a programmable controller (PC) 1, and detects abnormality of PC 1 from periodicity and regularity of the signals. A logic circuit 6 consists of an AND gate that makes the output of DFF 2 and the output of the unit 5 input, an inverter 8 that inverts the output of the unit 5 and an OR gate 9 that makes these output input. The unit 5 detects abnormality of PC 1 by periodicity and regularity of data and strobe signals, and blocks control signals from DFF 2 in the circuit 6. The signals of low level outputted from the unit 5 is inverted by the inverter 8 and becomes '1', and outputted to the plant/process 4 through the OR gate 9 as a signal that holds and controls it to safety side.
Inventors:
FUCHIGAMI KAZUYUKI
Application Number:
JP23453786A
Publication Date:
April 20, 1988
Filing Date:
October 03, 1986
Export Citation:
Assignee:
MITSUBISHI ELECTRIC CORP
International Classes:
G05B9/02; (IPC1-7): G05B9/02
Domestic Patent References:
| JPS5935202A | 1984-02-25 |
Attorney, Agent or Firm:
Hiroaki Tazawa