Synchronous serial communication network for controlling single point I/O devices

• US 5,802,321 A
• Filed: 06/20/1996
• Issued: 09/01/1998
• Est. Priority Date: 06/20/1996
• Status: Expired due to Fees

• Current Assignee: Square D Company (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Dowdy, Gary Lynn, Buda, Paul Robert
• Primary Examiner(s): Shin, Christopher B.
• Application Number:
  US08/667,286
• Time in Patent Office: 803 Days
• Field of Search: 340/825.05, 340/825.06, 340/825.15, 370/82.15, 370/94.1, 370/482, 370/483, 370/470-479, 395/200.5-200.8
• US Class Current: 709/251
• CPC Class Codes: G05B 19/0423 Input/output
• CPC Class Codes: G05B 19/4185 characterised by the network communication
• CPC Class Codes: G05B 2219/25178 Serial communication, data, also repeater
• CPC Class Codes: G05B 2219/25181 Repeater
• CPC Class Codes: G05B 2219/31127 Repeater between two networks
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A communication system between a programmable logic controller and a network of a plurality of remote input/output repeater modules uses a synchronous serial communications protocol. The programmable logic controller contains a transmitter module for generating a data packet containing the state of an output device connected to a remote input/output repeater module coupled to the network. A receiver module receives and decodes a returned modified data packet that indicates the state of input devices connected to the same or other remote input/output repeater modules also coupled to the network. The remote input/output repeater modules receive and decode the data packet to determine the state of the output devices that may be connected to it and modifies the data packet to indicate the state of its input device if there is one present. The modified data packet is sent to the next in-line remote input/output repeater module coupled to the network.

Claims

1. A control system for transferring data between devices connected on a synchronous serial communications network comprising:

(A) a first microprocessor based device having a data bus, a central processing unit (CPU) coupled to said data bus, a transmitter module coupled to said data bus and to said network, and a receiver module coupled to said data bus and to said network;

(B) a plurality of second devices consisting of remote input/output repeater (IOR) modules connected in series on said network, each of said plurality of IOR modules having a serial input for receiving a of said plurality of IOR modules having a serial input for receiving a data packet from a preceding device on said network, said preceding device being either said transmitter module or one of said plurality of IOR modules, a serial output for sending a modified data packet to a succeeding device on said network, said succeeding device being either said receiver module or one of said plurality of IOR modules having a serial input for receiving a data packet from a preceding device on said network, said preceding device being either said transmitter module or one of said plurality of IOR modules, an input terminal for connecting an input device, and an output terminal for connecting an output device;

(C) wherein said CPU executes a program, said program for controlling a plurality of output devices connected to said plurality of IOR modules by generating a plurality of output bytes in sequence, each of said output bytes respective for each of said plurality of IOR modules, and by coupling said output bytes over said data bus to said transmitter module for inclusion in said data packet without unique addressing of said output bytes, and wherein said transmitter module precedes a first of said plurality of IOR modules connected in series on said network and sends said data packet to said first IOR module;

(D) wherein each of said plurality of IOR modules extracts its respective output byte from said received data packet, said output byte for controlling energization and deenergization of an output device coupled to said output terminal, modifies said data packet by inserting an input byte representing a status of an input device coupled to said input terminal into said data packet, and sends said modified data packet to said succeeding device connected in series on said network;

(E) wherein said receiver module succeeds a last of said plurality of IOR modules connected in series on said network, and said last IOR module sends said modified data packet to said receiver module, said modified data packet containing said input bytes representing the state of each input device connected to said plurality of IOR modules; and

(F) wherein said receiver module extracts each of said input bytes from said modified data packet and sends said input bytes representing said status of each input device connected to said plurality of IOR modules and sends said input bytes over said data bus to said CPU for use in execution of said program for controlling said output devices.

2. The data packet sent from the transmitter module of claim 1 wherein said data packet consists of, in sequence, an input sync byte, an output sync byte, and n number of output bytes, where n is the number of said plurality of IOR modules connected on said network, and wherein each of said IOR module removes a first output byte immediately succeeding said output sync byte from said data packet, said output byte for controlling an output device coupled to said IOR module, and inserts said input byte immediately succeeding said input sync byte, said input byte for indicating a state of an input device coupled to said IOR module.

3. The modified data packet received by the receiver module of claim 1 wherein said data packet consists of, in sequence, an input sync byte, n number of input bytes, where n is the number of said plurality of IOR modules connected on said network, and an output sync byte and wherein said receiver module extracts said input bytes from said data packet and converts said input bytes to a parallel data bus for transfer to said PLC for use in execution of said program.

4. The data packet sent from the transmitter module of claim 1 wherein said output bytes are split-phase binary encoded to prevent said plurality of IOR modules from energizing and deenergizing said output devices if said output bytes are decoded by said IOR module as having two equal logic states.

5. The data packet received by the receiver module of claim 1 wherein said input bytes are split-phase binary encoded to prevent said program executing in said CPU from energizing and deenergizing said output devices if said input bytes are decoded by said receiver module as having two equal logic states.

6. The control system of claim 1 wherein said first microprocessor based device is a programmable logic controller.

7. The control system of claim 1 wherein said first microprocessor based device is a personal computer.

8. The control system of claim 1 wherein said synchronous serial communications network is a multiconductor wire cable and said data packet is transmitted over said cable.

9. The control system of claim 1 wherein said synchronous serial communications network includes a fiber optic cable and said data packet is transmitted over said fiber optic cable.