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US 5,508,910 AGranted
Redundant analog I/O board system
AssigneeForney International, Inc.
InventorRobert L. Diehl
Life of this patent
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AssigneeForney International, Inc.
InventorRobert L. Diehl
Estimating the term…
In a distributed logic control system, two duplicate analog I/O boards are provided to provide redundancy for the analog I/O boards. The analog I/O boards serve the function of applying analog output signals corresponding to received digital signals from a data processor to analog signal responsive units. Each analog I/O board has a microprocessor and two digital-to-analog converters and a analog-to-digital converter. The microcomputer determines whether the analog output signals generated by the digital-to-analog converters are within limits and, if they are not, it generates a fail signal applied to a programmable array logic circuit. Each analog I/O board includes a watch dog timer to indicate the sanity of the analog I/O board. The programmable array logic circuits respond to the failure conditions indicated by the watch dog timer and the microcomputer to select one of the analog I/O boards to be the operating analog I/O board to provide analog signals to analog signal responsive units.
A digitally responsive analog control system comprising a data processor, first and second analog I/O boards connected to receive digital signals representing analog values from said data processor, an analog signal responsive unit connected to each of said analog I/O boards for receiving an analog signal from said one of said analog I/O boards, a digital-to-analog converter on each of said analog I/O boards for converting digital signals to analog values, switch means on each of said analog I/O boards applying when enabled the analog signal from the digital-to-analog converter of the corresponding analog I/O board to said analog signal responsive unit and disconnecting when disabled the analog signal of the corresponding analog I/O board from said analog signal responsive unit, a microcomputer on each of said analog I/O boards for applying digital signals received by said analog I/O board to said digital-to-analog converter, a watch dog timer on each of said analog I/O boards to time out and generate an insanity signal if said watch dog timer is not strobed within a predetermined time interval of the preceding strobe of said watch dog timer, said microcomputer on each board comprising means to periodically strobe the watch dog timer on such board, and logic means on said first and second analog I/O boards to place one of said analog I/O boards in a non-operating state by disabling the switch means on said one of said analog I/O boards and to place the other one of said analog I/O boards in an operating state by enabling the switch means on said other one of said analog I/O boards, said logic means being responsive to the insanity signal generated by the watch dog timer on the operating analog I/O board to switch the operating analog I/O board to non-operating and to switch the operating analog I/O board to non-operating.
Dependencies are inferred from the claim text.