JP3090463B2 - Data communication system - Google Patents

Description

The present invention relates to a data communication system, and particularly to a data communication system for a vehicle.
The present invention relates to a data communication system suitable for use in an audiovisual (AV) system.

[Conventional technology]

In recent years, in-vehicle audio systems have evolved from systems that merely listen to music to systems that include visual elements. A system having not only audio but also visual functions is known as an AV system.

In-vehicle AV systems are constructed with various elements. For example, the audio element includes a cassette tape deck, a radio tuner, a CD (compact disc) player, and the visual element includes a TV.
(Television) A tuner, a navigation device, and the like are included. An audio reproduction signal output from each of these elements is reproduced from a speaker mounted in the vehicle via an amplifier, and an image reproduction signal is similarly output as an image on a display mounted in the vehicle. Today, each of these elements is controlled by digital technology, which is controlled by a microcomputer-based controller.

In order to operate each of the above elements systematically,
It is necessary to control each element comprehensively. Therefore, in the on-vehicle AV system, the controllers of the above elements are connected by a bus network, and mutual control data is transmitted and received via a communication bus constituting the network.

In a conventional network, each controller is controlled by a polling method. The polling method is a method in which one of the controllers is given a priority position, the controller is set as the master, and the remaining controllers are set as the master-slave relationship, and the master is always used when the master collects data from the slave. This is a method for accessing the slave side from the server.

When the master transmits and accesses communication data to the slave by the conventional polling method, or when the slave returns data to the master, it is necessary to identify or specify each controller. Therefore, an address indicating the controller is assigned to each controller.

In the conventional address assignment method, a unique address is assigned to each controller. The control data includes instruction data (for example, a start instruction: O
N data).

By the way, when transmitting and receiving communication data between the master and the slave, acknowledgment data (so-called ACK) is returned from the receiving side to the transmitting side to indicate that the transmission data has been correctly received. It has been known.
Further, as the processing on the transmitting side, there are cases where the acknowledgment data is confirmed and cases where it is not confirmed depending on the importance of the communication data. In an AV system, there are a plurality of slaves, and there are cases where a plurality of commands (a start command, a switching command, etc.) for each slave are continuously issued in communication data. In this case, according to the synchronous communication method, the correspondence between the command and the acknowledgment can be known on the command issuing side based on whether the communication timings match.

[Problems to be solved by the invention]

However, in the case of performing asynchronous communication, if a plurality of commands requiring an acknowledgment are successively issued, the command issuing apparatus cannot determine which command the acknowledgment data corresponds to. Therefore, it is not possible to determine whether or not the acknowledgment processing is necessary.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a data communication system capable of reliably responding to an issued command and acknowledgment data for the command.

[Means for solving the problem]

According to the first aspect of the present invention, a plurality of communication devices capable of issuing command data are connected to a communication bus, and one communication device communicates the command data via the communication bus. And the one communication device that has received the command data is a data communication system that returns response data corresponding to the transmitted command data, and the one communication device that transmits the command data is The communication device transmits command data including identification information indicating the communication device and identification information indicating a function of the communication device. One communication device that has received the command data transmits the identification information indicating the communication device and the communication device. The received command data is added to the response data including identification information indicating the function of the device, and the response data is returned. According to the second aspect of the present invention, in the data communication system according to the first aspect, the command data that requires the response data and the command data that does not require the response data are distinguished from each other. Is configured to change the processing of the transmission-side communication device in accordance with. According to a third aspect of the present invention, in the data communication system according to the first or second aspect, the communication device transmitting the command data includes identification information of a communication device to which the command data is transmitted. The communication device receiving the command data is configured to return response data including identification information of a communication device to which the response data is transmitted. Further, according to the invention described in claim 4, in the data communication system according to claims 1 to 3,
A communication device can be added to the communication bus. In FIG. 1, RDT ₁ is a command data (CM
Return data error detection data of the entire transmission data including D), RDT ₂ shows the response data error detecting data of the response data.

[Action]

According to the present invention, when a device (slave device or master device) on the command issuing side (sending side) transmits command data (CMD) requiring an acknowledgment, the receiving side device transmits the response data (ACK). The received command data (CMD) is added as it is to generate ACK + CMD response data, which is returned to the command issuing device. As a result, the command issuing device can determine which command is the response data (ACK) based on the added command data (CMD), and can determine whether to perform the acknowledgment process. . In addition, since the command data and the response data include the identification information of the communication device, the communication device of the transmission source can be specified. Also,
By separating commands that require an acknowledgment from those that do not, it is possible to reduce the occupation time of the communication bus due to data transfer, and to ensure high-speed asynchronous communication.

〔Example〕

Next, a preferred embodiment of the present invention will be described with reference to the drawings.

Power supply system of AV system The present invention is preferably applied to a vehicle-mounted AV system. As shown in FIG. 2, the AV system 103 receives power supply from the car battery 101 via the ACC switch 102. The ACC switch 102 is a switch that is linked to an engine key of the vehicle. By rotating the engine key to the position of the ACC switch 102, power is supplied to accessories in the vehicle. Therefore, in general, the power supply to the AV system 103 is repeatedly turned on / off each time the engine key is turned.

Example of Configuration of AV System FIG. 3 shows an example of the configuration of an AV system to which the present invention is applied. In the example of FIG. 3, a tape deck 6 for reproducing a recording signal from a cassette tape 1, a tuner 7 such as an FM for reproducing a radio wave received by an antenna 2, and a CD player for reproducing a recording signal from a CD 3 are used as an audio reproducing apparatus. 8
And a multi-CD player 9 including an auto-changer 5 for reproducing a recording signal from each CD of the multi-CD 4.
As the visual playback device, the TV received by antenna 2
A TV tuner (assumed to be built into the tuner 7) for reproducing radio waves or a CD-ROM 8
And a display 12 for outputting the recorded still image via the CD player 8. CD-RO
A typical example of using M is a navigation device. The external commander 10 includes a keyboard for inputting various operation commands from outside. The input device 13 can also be incorporated in the external commander 10.

Each of the above devices has a controller for controlling its own operation, and the controllers are connected to each other via a communication BUS 14 to form a bus-based control network. The structure of this network is shown in FIG. 4, and the details will be described later.

On the other hand, the reproduced signal of the audio reproducing apparatus is selectively input to the digital amplifier 16 via the selector 15 and is amplified by a predetermined amount and then emitted from the speaker 17. A digital signal circuit included in the digital amplifier 16 is also controlled by a built-in controller, and this controller is also connected to the communication BUS.

AV System Control Network FIG. 4 shows an example of an AV system control network. Here, for convenience of explanation, in FIG.
Each device connected to S14 is referred to as a “unit” as a general expression. As shown in FIG. 4, each unit is connected to the communication BUS 14 in parallel. One of the units is referred to as a “master” in order to control the entire network, and this is indicated by a master unit 200. Are all other remaining units "slave", these slave units 200 _-1 to 200
Shown by _-n .

Master controller 1 built in master unit 200
8 is connected to the communication BUS 14 via the communication interface IC25. In this example, the master controller 18 also controls the tape deck 6 and the tuner 7. Further, the control section of the tape deck 6 of the master controller 18 also controls the autochanger 5. Slave unit 200 _-1 to 2
Each of the slave controllers 19 to 24 built in 00- _n is similarly connected to the communication BUS 14 via the communication interface ICs 25 to 31.

FIG. 5 shows the master unit 200 and the slave unit 200.
A specific example of the connection state with _-n is shown. As shown in FIG.
Communication BU between master unit 200 and slave unit 200- _n
Connected by S14. The communication BUS 14 uses a twisted pair line composed of two lines. The communication data DT transmitted and received via the communication BUS 14 is transmitted to the communication interface IC 25 of the master unit 200 and the slave unit 200- _n.
And the communication interface IC31. The communication interface IC 25 is a communication driver / receiver 32
Similarly, the communication interface IC31 is separated into a communication driver / receiver 35 and a communication control IC36. In this regard, in the related art, it has been provided integrally in one IC. The communication control IC 33 is formed of CMOS transistors and has a communication driver /
The receiver 32 is formed of a bipolar transistor having a high current driving capability. The same applies to the communication driver / receiver 35 and the communication control IC 36.

Thus, regarding the communication interface IC 25, the communication control IC 33 and the communication driver / receiver 32
This makes it possible to cope with a change in the transmission medium of the communication BUS 14. For example, in the example of FIG.
Although a twisted pair wire is used as the communication BUS 14 for differential transmission, as shown in FIG. 6, when an optical communication cable 40 is used as the communication BUS 14, a communication driver / receiver
By using the electro-optical converter 38 instead of 32, it is possible to cope without changing other configurations. Further, the operation failure generated in the master unit 200 is largely due to disturbance noise mixed in from the communication BUS 14, and even if an excessive signal is mixed in for some reason, the communication driver / receiver 32 alone often fails. /
By replacing only the receiver 32, it is easy to return to the current state, which is advantageous for maintenance. In particular, for automotive
In the case of an AV system, there are many opportunities to mix noise generated from the engine system of an automobile, so that it is effective.

Also, from the viewpoint of IC manufacturing, it is easier to manufacture the IC and the cost is more advantageous if the CMOS transistor and the bipolar transistor having different manufacturing processes are separated from each other than the configuration of the Bi-CMOS IC. .

Incidentally, the above description has described a communication interface IC 25, and is separated into a communication driver / receiver and the communication control IC Similarly for communications interface IC26~31 the other slave units 200 _-1 to 200 DEG _-n.

Next, the transmission format of the communication data DT used in the present invention will be described.

FIG. 7 shows an example of a transfer format of the communication data DT. As shown in FIG. 7, the communication data DT, the master address data MA from the head indicates the address of the master unit 200, slave address SA indicating the addresses of the slave knit 200 _-1 to 200 DEG _-n, the message length of data D It comprises message length data N, classification data TP indicating the type of data D, and data D indicating transfer contents.

The configuration of the data D is the content of the communication data DT,
It differs depending on the classification data TP, and is roughly classified into three types of format configurations. As shown in FIG. 10, the first format is a format for confirming connection, the second format is a format for keys, display data, and the like, and the third format transmits a result of a checksum CS. Format. Furthermore, the format for confirming the connection is to transfer the communication data DT to the slave units _200-1 to 200-2.
The transfer from 00 _-n to the master unit 200 is different from the transfer from the other unit. In FIG. 10, the format of the key and the display data is the same from the physical status data PS to the logical mode data LM in the data configuration, and is not shown.

The classification data TP is a data area which is arranged at the head of the communication data DT and indicates the type of data D following the classification data TP. The classification data TP is composed of large classification data and small classification data. The major classification data is as shown in FIG.
Indicates the type of data D. Bit combination is classified data TP
If the whole is 8 bits, the upper 4 bits are assigned. As shown in FIG. 9, the small classification data is mainly used to identify the format of the data D, and the lower 4 bits are allocated.

Physical address data PA is Figure 11, as shown in FIG. 12, the communication interface of the master unit 200 to slave unit 200 _-1 to 200 DEG _-n on the communication BUS 14 IC25～
This is an address in communication for specifying 31 and is an address indicating the master unit 200 and the slave units 200 _-1 to 200 _-n . Of the physical address data PA, the physical address data PA that specifies the master unit 200 is always fixed. As for the physical address data PA, basically, one physical address data PA is assigned to one unit. FIG. 14 shows an example in which physical address data PA is allocated in association with the unit configuration shown in FIG. In addition,
In FIG. 14, physical address data PA is also set in the master controllers 18 to 24. This is because, like the master unit 200, two functional elements of the tape deck 6 and the tuner 7 are provided in one controller master controller 18. Is connected. In a combination of one controller and one function, the physical address data PA and the logical address data LA have the same address as in the slave controllers 19 to 24.

The physical status data PS is status information relating to the master unit 200 and the slave units 200 _-1 to 200 _-n , and includes a functional address (that is, logical address data L to be described later) of the unit.
This is data indicating the number of A).

As shown in FIG. 13, the logical address data LA is data indicating the functions (that is, tuners and tape decks) of the master unit 200 and the slave units 200 _-1 to 200 _-n. Assigned for each function. The number of logical address data LA is equal to the number of functions of the controller determined by the physical address data PA.
LA _1, LA ₂ ... not a constant number because The added so on. FIG. 14 shows an example in which logical address data LA is allocated in association with the unit configuration in FIG.

The talker address data TL indicates the address of the transmission source (speaker) transmitting the communication data DT.

The listener address data LN indicates an address of a transmission destination (listener) for receiving the communication data DT.

The logical status data LS contains each logical address.
Indicates the state of the function corresponding to LA.

The logical mode data LM indicates an operation state (mode) of a function corresponding to each logical address.

The checksum data CS is data for error detection added in order to improve the reliability of the data D.

By the way, the master unit 200 and the slave unit 200
The contents of the communication data DT transmitted and received between _-1 to 200 _-n are:
Determined by the classification data TP (see FIGS. 7 and 10)
The types are as shown in FIG. Command data CMD is included in these communication data DT. The command data CMD includes, for example, a key command TP = 3H, a system command TP = 4H, a special command TP = 5H, as shown in FIG. These command data CMD are transmitted to the slave units 200 _-1 to 200 connected to the communication bus 14.
_-n , the command data CM
You need to check if D was sent correctly. Therefore, for the system command (TP = 40H), which is important command data CMD, the receiving side (slave unit 200)
Acknowledgment data ACK is returned from _-1 to 200 _-n or master unit 200). Also, the key command (TP = 30
H), the special command (TP = 50H) checks the checksum.

The acknowledgment data ACK is, as shown in the upper part of FIG. 15,
Are represented by logical status data LS ₁ , LS _2, ... Added to the rear of the classification data TP, physical status data PS, talker address TL, and listener address LN. LM is logical mode data. Talker address TL indicates the address of the sender (speaker) of command data CMD, and listener address LN indicates the command data
Indicates the address of the receiver (listener) of the CMD. The sender and the receiver are specified by the talker address TL and the listener address LN, and a correct acknowledgment is made.

However, when a plurality of system commands in the command data CMD are continuously transmitted, or in the case of asynchronous communication, the command source transmits the returned acknowledgment data ACK.
May not be able to determine which command data CMD corresponds to the system command.

Therefore, as shown in the lower part of FIG. 15, the system command in the command data CMD sent to the classification data TP is completely added, and the checksum data CS is added thereto to generate echo back data. You are to reply.

As described above, by adding the system command in the transmitted command data CMD to the acknowledgment data ACK and generating and returning echo back data, the system command in the command data CMD included in the echo back data is generated. Based on the system command in the transmission command data CMD and the acknowledgment data AC for it
Since a match with K can be determined, even a plurality of consecutive commands can be correctly determined.

It should be noted that adding the system command in the command data CMD to the acknowledgment data ACK also increases the data length, thereby increasing the transmission time. Therefore, important commands (system commands) and non-important commands (key commands, special commands) are distinguished.
Echo back data can be returned only for important commands.

Communication operation In the AV system described above, the master unit 20
Communication data D between 0 and slave units 200 _-1 to 200 _-n
The operation when communicating T will be described below.

FIG. 16 shows a specific example thereof. FIG. 16 shows an example of a connection confirmation sequence when the slave unit including the TV / FM tuner and the master unit access the own AV system from the slave unit to confirm the connection.

In this network, unlike the conventional polling method, all slave units self-declare their own units to the master unit. The master unit does not actively access the slave unit.

Now, in FIG. 16, because the slave unit is connected confirmation request (self-reported), to transmit to the master unit via the communication BUS14 issue the communication data DT _1. At this time, the communication data DT ₁ sets its own physical address data PA to “1”.
23H "(H is hexadecimal hexadecimal), the physical address data PA of the master unit of the other party is set to" 100H ", and the logical address data indicates that its own slave unit has a configuration including a TV tuner and an FM / AM tuner. This is indicated by LA ₁ = 05 and logical address data LA ₂ = 07. (See Fig. 13.) The communication data DT ₁ allows the master unit 200 to set PA = 123H and LA
It is registered that a device having the functions of ₁ = 05 and LA ₂ = 07 has been connected to the communication BUS 14, and this device will be handled as an AV system member thereafter. Master unit, when the communication data DT ₁ is sent to indicate that it has received the communication data DT _1, and returns the return data RDT ₁ to the slave unit. Then, the slave unit which is newly connected, for notify the constituent members of the AV system, and transmits the system connection information DT ₂ to the slave unit side. The slave unit that has received the system connection information DT ₂ for acknowledgment, and returns the return data RDT ₂ to the master unit side. Then, after a lapse of a predetermined time,
Slave unit transmits communication data DT ₁ connection confirmation request (self-reported) to the master unit side again. In the case of an in-vehicle AV system, the transmission of the connection confirmation request communication data DT ₁ again after a predetermined time has elapsed is performed by turning on / off the power supply.
Because the FF depends on the ON / OFF of the ACC switch, it is necessary to check the connection periodically.

As described above, the communication data DT always includes the physical address data PA and the logical address data LA, and the physical address data PA and the logical address data LA are mutually independent data. The communication data DT can be transmitted to any destination.

In the above operation example, an example of communication between the slave unit and the master unit has been described, but communication can be similarly performed between other slave units.

In addition, the format of the communication data DT and the assignment of addresses to each unit
By separately performing the PA and the logical address LA, even if the physical address PA is unknown, if the logical address LA is clearly set, it is possible to connect a new unit, and the new unit can be connected. Communication between the main unit and the already connected unit is possible.

That is, it is assumed that a new slave unit 200- _m is connected to the communication BUS 14, as shown in FIG. In this case, even if the physical address data PA of the slave unit 200- _m is not assumed and the physical address data PA is 101, if the function is the “display function”, it is already registered in the slave unit 200. Since the same function exists with the logical address data LA = 01, the logical address data LA can be accessed, so that the slave unit 200- _m can be connected. This means that A
This will contribute to improving the scalability of the V system.

Next, FIG. 18 shows a sequence example in the case where an ON command which is a system command (TP = 40H) is transmitted from the master unit side to the slave unit side. In FIG. 18, ON for turning on the tuner from the master to the tuner
The communication data including the command (02) is transmitted. When receiving the communication data, the tuner returns return data for confirming reception. Further, the tuner transmits acknowledgment data ACK for indicating command reception to the master side. At this time, the command is an important system command (TP
= 40H), the acknowledgment data ACK is returned with the echo back data EB added thereto. The structure of the echo back data EB is shown in FIG. Next, the master unit transmits return data for the acknowledgment data ACK to the tuner which is a slave.

〔The invention's effect〕

As described above, according to the present invention, when the device on the command issuing side transmits the command data, the receiving side device adds the transmitted command data as it is to the response data to generate echo back data, Reply to device. As a result, the command issuing device can determine what command is the response data based on the added command data, and can ensure the high speed of the asynchronous communication.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a power supply system diagram of an AV system, FIG. 3 is an overall configuration diagram of the AV system, FIG. 4 is a block diagram of a control network of the AV system, and FIG. FIG. 6 is a block diagram showing a specific example of a connection state between a master unit and a slave unit. FIG. 6 is a block diagram showing another example of a connection state between a master unit and a slave unit. FIG. 7 is an explanatory diagram showing a transfer format of communication data. , FIG. 8 is an explanatory diagram showing the contents of the classification data (major classification), FIG. 9 is an explanatory diagram showing the contents of the classification data (small classification), FIG. 10 is an explanatory diagram showing the basic data format, FIG. Is an explanatory diagram showing an example of a physical address, FIG. 12 is an explanatory diagram showing an example of a physical address, FIG. 13 is an explanatory diagram showing an example of a logical address, and FIG. 14 shows an example of allocation of a physical address and a logical address. Block Diagram Figure 15 is an explanatory diagram showing the format of the echo back data, FIG. 16 is an explanatory view showing an example of a communication operation, FIG. 17 is an illustration of an effect of the present embodiment. FIG. 18 is an explanatory diagram showing an example of echo back of a system command. ADR: Address data B: Communication BUS CS: Check sum data CMD: Command data D: Data DT: Communication data EB: Echo back data LA, LA _{1 to} LA _n: Logical address data LN ₁ ...... listener address M ...... master device PA, PA ₁ ~PA _n ...... physical address data PS ...... physical status data S ₁ to S _n ...... slave device TP ...... classification data TL ...... talker address 101 Car battery 102 ACC switch 103 AV system 200 Master unit 200 _-1 to 200 _-n Slave unit 1 Cassette tape 2 Antenna 3 CD 4 Multi CD 5 …… Auto changer 6 …… Tape deck 7 …… Tuner 8 …… CD player 9 …… Multi CD player 10 …… External commander 11 …… Display 12 …… Display 13 …… Input device 14 ... Communication BUS 15 ... Selector 16, 16A ... Digital amplifier 17 ... Speaker 18 ... Master controller 19 ... Slave controller 20 ... Slave controller 21 ... Slave controller 22 ... Slave controller 23 ... Slave controller 24 ... … Slave controller 25 …… Communication interface IC 26 …… Communication interface IC 28 …… Communication interface IC 29 …… Communication interface IC 30 …… Communication interface IC 31 …… Communication interface IC 32 …… Communication driver / Receiver 33 ... communication control IC 34 ... controlled part 35 ... communication driver / receiver 36 ... communication control IC 37 ... controlled part 38 ... electrical / optical converter 39 ... electrical / optical converter

────────────────────────────────────────────────── (5) References JP-A-60-220645 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 12/28

Claims (4)

(57) [Claims] A plurality of communication devices capable of issuing command data are connected to a communication bus, one communication device transmits the command data via the communication bus, and one communication device receives the command data. In a data communication system in which a communication device returns response data corresponding to the transmitted command data, one communication device transmitting the command data indicates identification information indicating the communication device and a function of the communication device. And transmitting the command data including the identification information. The one communication device that has received the command data transmits the command data to the response data including the identification information indicating the communication device and the identification information indicating the function of the communication device. A data communication system configured to reply with the received command data added thereto. 2. The data communication system according to claim 1, wherein the command data requiring the response data and the command data not requiring the response data are distinguished from each other, and the transmitting-side communication device is determined according to the command data. A data communication system characterized by changing the processing of (1). 3. The data communication system according to claim 1, wherein the communication device transmitting the command data transmits command data including identification information of a communication device to which the command data is transmitted. A communication device receiving the command data, wherein the communication device is configured to return response data including identification information of a communication device to which the response data is transmitted. 4. The data communication system according to claim 1, wherein a communication device can be added to said communication bus.