Data transmission system

• US 5,113,410 A
• Filed: 01/26/1990
• Issued: 05/12/1992
• Est. Priority Date: 06/16/1983
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hasegawa, Akira, Oho, Shigeru, Hirayama, Takeshi, Hamano, Fumio
• Primary Examiner(s): Chin, Stephen
• Application Number:
  US07/470,776
• Time in Patent Office: 837 Days
• Field of Search: 375/7, 375/8, 375/36, 371/48, 371/53, 340/825.5, 340/825.51, 340/825.06, 340/825.07, 340/825.08, 364/420.01, 370/85.1, 370/85.11
• US Class Current: 375/219
• CPC Class Codes: B60R 16/0315 using multiplexing techniques multiplexing for transmission of signals G08C15/00; multiplexing for electrical communication in general H04J
• CPC Class Codes: G06F 13/12 using hardware independent of the central processor, e.g. channel or peripheral processor
• CPC Class Codes: G06F 13/24 using interrupt G06F13/32 takes precedence
• CPC Class Codes: Y10S 370/908 Local area network

Abstract

In a data transmission system having a central control unit including a data processing unit (MPU) and a communication control unit (CIM) which is capable of transmitting data to a local control unit (LCU) in a half duplex mode, the data processing unit receives the data in an interruption based on an end of data reception signal supplied from the communication control unit. At the time of initialization of the system, the central control unit responds to the application of power to the system by transmitting predetermined control data to the local control unit to set the state of accessory devices connected thereto, thereby preventing improper operation of the accessory devices during system startup.

Claims

1. In a data transmission system including a central control unit having a data processing unit and a communication control unit, and a plurality of local control units, wherein data transmission is effected between said central control unit and the local control units vis a communication medium, a method of initializing the system when power is turned on, comprising the steps of:

(a) setting a system start flag in the central control unit in response to turning on the power of the system;

(b) transmitting predetermined control data from said communication control unit to a local control unit;

(c) detecting reception of monitor data from the local unit in response to reception of said control data;

(d) retransmitting said control data to the local control unit when the monitor data is not received;

(e) generating an alarm when monitor data is not received from the local unit in response to the retransmission of said control data;

(f) repeating steps (b) to (e) for every other local control unit;

(g) clearing said system start flag after having transmitted the control data to all local control units; and

(h) transmitting other prepared control data to each of the local control units.

2. A method according to claim 1, wherein said central control unit prepared said other control data upon receiving monitor data from a local control unit through said communication control unit, and sends selected monitor data to a display panel for displaying the data.

3. A data transmission system for an automobile, comprising:

a first local control unit connected to an input device, said first control unit including means for transmitting monitor data containing information of a state of the input device;

a second local control unit connected to an accessory device, said second local control unit controlling the accessory device in accordance with received control data; and

a central control unit for determining control of the accessory device based on information concerning the input device contained in monitor data received from said first local control unit and for transmitting control data incorporating information for the determined control to said second local control unit;

said central control unit including;

(a) means for starting the system by applying power thereto; and

(b) means, after the starting of said system and before receiving monitor data from the first local control unit, for transmitting predetermined control data for controlling said accessory device to a predetermined state.

4. A system according to claim 3, wherein said first local control unit for transmitting monitor data containing information of a state of the input device and said second local control unit for controlling said accessory device are constituted as a single unitary unit.

5. A system according to claim 3, wherein said first local control unit for transmitting monitor data containing information of a state of the input device, and said second control unit for controlling the accessory device are connected to each other by a collective wiring system.

6. A system according to claim 5, wherein said central control unit transmits control data incorporating an address representing a particular one of said first and second local control units.

7. A system according to claim 5, wherein said particular one of said first and second local control units transmits monitor data upon receiving said control data.

8. A data transmission system in an automobile comprising:

a first local control unit connected to an input device, and including means for transmitting monitor data containing information of a state of the input device;

a second local control unit connected to an accessory device, controlling the accessory device in response to received control data; and

a central control unit for determining control of the accessory device based on information of the input device contained in monitor data received from said first local control unit and for transmitting to said second local control unit control data incorporating information for the control of the accessory device;

said central control unit including;

(a) means for starting said system by applying power thereto; and

(b) means, after the starting of said system and independent of the state of the input device, for transmitting to said second local control unit predetermined control data for controlling said accessory device to a predetermined state.

9. A data transmission method for an automobile, having a first local control unit connected to an input device, said first control unit including means for transmitting monitor data containing information of a state of the input device;

a second local control unit connected to an accessory device, said second local control unit controlling the accessory device in accordance with received control data; and

a central control unit for determining control of the accessory device based on information concerning the input device contained in monitor data received from said first local control unit and for transmitting control data incorporating information for the determined control to said second local control unit;

the method performed by said central control unit comprising the steps of;

(a) starting the system by applying power thereto; and

(b) after the step (a) and before receiving monitor data from the first local control unit, transmitting predetermined control data for controlling said accessory device to a predetermined state.

10. A method according to claim 9, wherein said first local control unit for transmitting monitor data containing information of a state of the input device and said second local control unit for controlling said accessory device are constituted as a single unitary unit.

11. A method according to claim 9, wherein said first local control unit for transmitting monitor data containing information of a state of the input device, and said second control unit for controlling the accessory device are connected to each other by a collective wiring system, further including transmitting from said central control unit control data incorporating an address representing a particular one of said first and second local control units.

12. A method according to claim 11, wherein said particular one of said first and second local control units transmits monitor data upon receiving said control data.

13. A data transmission method for an automobile, having a first local control unit connected to an input device, and including means for transmitting monitor data containing information of a state of the input device;

a second local control unit connected to an accessory device, controlling the accessory device in response to received control data; and

a central control unit for determining control of the accessory device based on information of the input device contained in monitor data received from said first local control unit and for transmitting to said second local control unit control data incorporating information for the control of the accessory device;

the method performed by said central control unit comprising the steps of;

(a) starting said system by applying power thereto; and

(b) after the step (a) and independent of the state of the input device, transmitting to said second local control unit predetermined control data for controlling said accessory device to a predetermined state.