Analog multiplexer control circuit

• US 4,146,750 A
• Filed: 12/29/1977
• Issued: 03/27/1979
• Est. Priority Date: 12/29/1977
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Spiesman, Robert L.
• Primary Examiner(s): Robinson, Thomas A.
• Application Number:
  US05/865,383
• Time in Patent Office: 453 Days
• Field of Search: 179/15 A, 179/15 BL, 340/183, 340/347 DD
• US Class Current: 370/537
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

An improved multiplexer circuit features an addressing arrangement for effecting the selection, first, of the particular multiplexing module, then of an individual input from among the several inputs to the module. To this end, a latch assembly is provided for storing the address of the individual input to the module. Gating structure is provided, responsive to an address code for enabling the latch assembly to store the applied address code. An output switch is connected in the output circuit of the multiplexer module and operatively controlled by the selecting circuit to block any spurious output from the multiplexer module when the particular multiplexer is not selected.

Claims

1. A digital computer based process control system including an analog input multiplexer control circuit and digital computer means for supplying digital control signals to said multiplexer control circuit, said multiplexer control circuit comprising:

a selectively controlled multiplexer module having a plurality of pairs of analog signal input terminals, a single pair of analog signal output terminals, and signal responsive input selection control terminals;

digital signal responsive logic control means for controlling the operation of said multiplexer module;

said logic control means including a latch assembly means for storing address signals received from said computer means and signal responsive gating means for controlling the operation of said latch assembly means;

said gating means being responsive to further address and control signals from said computer means to provide control signals for said latch assembly means;

said latch assembly means also including latch means for storing a signal derived from said further address and control signals to provide a controlled "enable" signal for said multiplexer module;

signal responsive solid state switch means connected serially to said output terminals of said multiplexer module; and

means connecting the output of said last mentioned latch means of said latch assembly means to said solid state switch means to control the operation thereof.

2. A digital computer based process control system including an analog input multiplexer control circuit and digital computer means for supplying digital control signals to said multiplexer control circuit, said multiplexer control circuit comprising:

a selectively controlled multiplexer module having a plurality of pairs of analog signal input terminals, a single pair of analog signal output terminals, and signal responsive input selection control terminals;

digital signal responsive logic control means for controlling the operation of said multiplexer module;

said logic control means including a latch assembly means for storing address signals received from said computer means and signal responsive gating means for controlling the operation of said latch assembly means;

said gating means being responsive to further address and control signals from said computer means to provide control signals for said latch assembly means;

said latch assembly means having output means for said stored address signals and means connecting said input selection control terminals of said multiplexer module to said latch assembly output means;

said latch assembly means also including latch means for storing a signal derived from said further address and control signals to provide a controlled "enable" signal for said multiplexer module;

signal responsive solid state switch means connected serially to said output terminals of said multiplexer module; and

means connecting the output of said last mentioned latch means of said latch assembly means to said solid state switch means to control the operation thereof.

3. A digital computer based process control system including an analog input multiplexer control circuit and digital computer means for supplying digital control signals to said multiplexer control circuit, said multiplexer control circuit comprising:

a selectively controlled multiplexer module having a plurality of pairs of analog signal input terminals, a single pair of analog signal output terminals, and signal responsive input selection control terminals;

digital signal responsive logic control means for controlling the operation of said multiplexer module;

said logic control means including a latch assembly means for storing address signals received from said computer means and signal responsive gating means for controlling the operation of said latch assembly means;

said gating means being responsive to further address and control signals from said computer means to provide control signals for said latch assembly means;

said latch assembly means having output means for said stored address signals and means connecting said output means to said input selection control terminals of said multiplexer module;

said latch assembly means also including latch means for storing a signal derived from said further address and control signals to provide a controlled "enable" signal for said multiplexer module.

4. A digital computer based process control system including an analog input multiplexer control circuit and digital computer means for supplying digital control signals to said multiplexer control circuit, said multiplexer control circuit comprising:

a selectively controlled multiplexer module having a plurality of pairs of analog signal input terminals, a single pair of analog signal output terminals, and signal responsive input selection control terminals;

digital signal responsive logic control means for controlling the operation of said multiplexer module;

said logic control means including a latch assembly means for storing address signals received from said computer means and signal responsive gating means for controlling the operation of said latch assembly means;

said gating means being responsive to further address and control signals from said computer means to provide control signals for said latch assembly means;

said latch assembly means having output means for said stored address signals and means connecting said output means to said input selection control terminals of said multiplexer module;

said latch assembly means also including further latch means for storing a signal derived from said further address and control signals to provide a controlled "enable" signal for said multiplexer module; and

output circuit means including further gating means connecting an output for said stored further address and control signal to an "enable" input terminal on said multiplexer module.

5. A multiplexer control circuit as set forth in claim 4 wherein said further gating means is enabled by an external signal from said computer means.

6. A digital computer based process control system including an analog input multiplexer control circuit and digital computer means for supplying digital control signals to said multiplexer control circuit, said multiplexer control circuit comprising:

a selectively controlled multiplexer module having a plurality of pairs of analog signal input terminals, a single pair of analog signal output terminals, and signal responsive input selection control terminals;

digital signal responsive logic control means for controlling the operation of said multiplexer module;

said logic control means including a latch assembly means for storing address signals received from said computer means and signal responsive gating means for controlling the operation of said latch assembly means;

said gating means being responsive to further address and control signals from said computer means to provide control signals for said latch assembly means;

said latch assembly means having output means for said stored address signals and means connecting said output means to said input selection control terminals of said multiplexer module;

said latch assembly means also including further latch means for storing a signal derived from said further address and control signals to provide a controlled "enable" signal for said multiplexer module, output circuit means including further gating means connecting an output for said stored further address and control signals to an "enable" input terminal on said multiplexer module;

signal responsive solid state switch means connected serially to said output terminals of said multiplexer module; and

means connecting the output of said last mentioned latch means of said latch assembly means to said solid state switch means to control the operation thereof.