JPH0644171A - Multi-drop communication control system - Google Patents

Abstract

PURPOSE:To simplify circuit configuration and control processing by dispensing with a control channel other than a speech channel at the time of transmitting up data from multi-drop terminal equipment in response to a polling request, etc., from multidrop host equipment. CONSTITUTION:A DIU 5b transmits a data frame to a CX-MAC 11b only when an RS line is ON, and the CX-MAC 11b retrieves always the presence of data in a transmitting buffer 200b. When the data is detected in the transmitting buffer 200b, the CPU 100b of the CX-MAC 11b sets a transmission MAP 201b so as to transmit the data in the transmitting buffer 200b to a trunk line LAN by putting it on a frame 202b, and when the data comes not to be detected in the transmitting buffer 200b, it resets the transmission MAP 201b so as to halt data transmission to the trunk line LAN.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention connects a multi-drop host device to one node of a trunk LAN via interface means, and similarly connects multi-drop terminal devices to other nodes. The present invention relates to a multi-drop communication control method for realizing 1-to-n communication between the host device and a plurality of terminal devices in the data communication system.

[0002]

2. Description of the Related Art FIG. 4 is a general system configuration diagram of a data communication system to which a multi-drop communication control system is applied. As shown in the figure, in this data communication system, a multi-drop host device 6 is connected to one node 3a of a trunk LAN 1 via a terminal interface (DSTI) 4a and a data interface unit (DIU) 5a, and at the same time. The DSTI 4 is connected to each of the plurality of other nodes 3b, 3c, 3d of the trunk LAN 1.
b, 4c, 4d and DIUs 5b, 5c, 5d are connected to the multi-drop terminal devices 7b, 7c, 7d.

In this data communication system, in response to a polling request from the host device 6, each terminal device 7b,
The processing operation according to the conventional communication control method when 7c and 7d return a response will be described with reference to FIG.

Here, FIG. 5 is a detailed configuration of the node 3b in the data communication system shown in FIG. 4 (node 3c,
3d also has the same configuration) and the peripheral connection relationship. In FIG. 5, the node 3b is
To the DIU 5b-1,
Two terminal devices (DTE) 7b via the DIU 5b-2
It is shown that -1, 7b-2 are connected.

As shown in the figure, the node 3b comprises a node basic unit 10b and a CX-MAC 11b which is an interface between the trunk LAN 1 and the DSTI. Furthermore,
CX-MAC 11b is CPU 100b, network clock I /
F unit 101b, communication path I / F unit 102b, DSTI I
The I / F unit 103b and the control path I / F unit 104b are provided.

This structure is the same in the other nodes 3c and 3d, and conventionally, the CX-MA of each of these nodes has been conventionally used.
Be sure to use the control path I / F 104b in C11b (see FIG. 5).
Was provided. As will be described later, the control path I / F 104b has a functional configuration that serves as an interface with a control path that handles control data for securing a communication path for transmitting data.

For example, when the terminal device 7b-1 transmits response data (uplink data communication) to the data (downlink data communication) sent from the host device 6 at the time of the polling request or the like, the terminal device 7b- First in R
Turn on the S line (transmission request line). At that time, DIU5b
-1 is a command signal indicating that the RS line is ON (LCG
RSON) to the CX-MAC 11b.

Next, in the CX-MAC 11b, the CPU 100b which has received the LCGRSON through the control path I / F 104b secures a path (communication path) required for data signal transmission, and sends an affirmative response to the DIU 5b-1 ( ACK) is returned.

Upon receiving the ACK, the DIU 5b-1 sends an update message (RS = 1) to the DIU 5a accommodating the host device 6 to turn on the CD line of the DIU 5a, and after a certain time, the DIU 5b-1 turns on the CS line. Turn it on. Then, when the CS line is turned ON, the terminal device 7b-1 starts the upstream data communication. Main LAN
For 1, the update message and the response are the same signal and are processed in exactly the same way.

When the upstream data communication ends, the terminal device 7b
-1 turns off the RS line, and DIU5
b-1 transmits an update message (RS = 0) and turns off the CD line of the DIU 5a. And so on
Host device 6 and each terminal device 7b-2 or 7c, 7d
Data of a polling request and its response is transmitted and received between and.

According to this conventional multi-drop communication control system, when performing upstream data communication, a control path for transmitting and receiving a control command for securing this communication path is necessary in addition to the communication path for data signals. . Therefore, in order to control this control path, the control path I / F described above must be provided in the CX-MAC of each node without fail, which complicates the circuit configuration and complicates the control method. I didn't get it.

[0012]

As described above, in the above-described conventional multi-drop communication control method, since the terminal device which should respond as a result of downlink data communication performs uplink data communication, R
When the S line is turned ON, the DI corresponding to the response terminal device
When U sends LCGRSON to CX-MAC of the corresponding node, and then this DIU receives ACK indicating the result that the communication path is secured by CX-MAC, after sending an update message (RS = 1) to the host-side DIU Since the DIU turns on the CS line after a certain time and starts the upstream data communication from the response terminal device, when performing the upstream data communication from the response terminal device, the LCGRSON ON / OFF command is issued separately from the communication path. Receive and A
There is a problem that a control path for transmitting the CK command is required, the circuit configuration becomes complicated, and at the same time, its control becomes complicated.

The present invention eliminates this problem, and when transmitting uplink data from a multi-drop terminal device in response to a polling request from a multi-drop host device,
An object of the present invention is to provide a multi-drop communication control system that does not require a control path different from a communication path and can simplify the circuit structure and communication control.

[0014]

According to the present invention, a multi-drop host device is connected to one node of a trunk LAN via a terminal interface and a data interface unit, and the same applies to other nodes of the trunk LAN. 1 or more multi-drop terminal devices are connected to each other via a terminal interface and a data interface unit, and 1 is provided between the host device and each of the terminal devices.
In the data communication system for performing the communication with respect to n, each of the nodes stores a transmission buffer for temporarily storing the data received from the data interface unit of each of the terminal devices, and the contents of the transmission buffer on the frame of the trunk LAN. At least a transmission MAP for loading in a certain time slot is provided, and it is constantly searched whether or not the response data sent from each terminal device in response to the reception of the inquiry data from the host device exists in the transmission buffer. However, when there is data in the transmission buffer, the transmission MAP is set to transmit the data to the trunk LAN, and when there is no data in the transmission buffer, the transmission MAP is reset and the trunk L
It is characterized by controlling to stop data transmission to the AN.

[0015]

In the present invention, the RS line of the terminal device is turned on / off.
DIU (data interface unit) for controlling the start / stop of data frame transmission when the
The software and the transmission buffer for storing the data received from the DIU and transmitting it to the trunk LAN are searched, and when the data is detected in this transmission buffer, the transmission for putting the data in the time slot of the frame on the trunk LAN. The CX-MAC software for setting the MAP and resetting the transmission MAP when no data is detected is used to control the upstream data communication from the terminal device to the host device.

Specifically, in this communication control system, when the terminal device turns on the RS line to send a response to the host device, the DIU starts transmitting a data frame to the CX-MAC, and the CX-MAC Then, the received data from the DIU is temporarily stored in the transmission buffer before being transmitted to the trunk LAN. After that, the CX-MAC constantly searches the transmission buffer, and when data is detected in the transmission buffer, the transmission MAP is set to transmit the data in the transmission buffer to the trunk LAN, and the data is detected in the transmission buffer. If it is no longer possible, the transmission MAP is reset to stop the data transmission to the trunk LAN.

According to this communication control method, during uplink data communication, a control path for receiving the LCGRSON / OFF command and transmitting the ACK command is not necessary in addition to the communication path. That is, according to the present invention, the control path I / F which has been conventionally required can be removed from the CX-MAC, and thus the circuit structure and the control process can be simplified.

[0018]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a main configuration of a data communication system to which the multi-drop communication control system of the present invention is applied.

Here, a data communication system having a configuration as shown in FIG. 4 is assumed as a system to which the multi-drop communication control system of the present invention is applied. The above-mentioned FIG. 1 particularly shows the detailed configuration of the node 3b on the trunk LAN 1 of this data communication system and the DSTI 4b and DIU 5 between the node 3b and the terminal devices 7b-1 and 7b-2.
This is a disclosure of the connection relationship via b-1 and 5b-2.

The trunk LAN 1 is connected to each other via a transmission line 2 and is connected to the DSTIs 4c, 4 respectively.
The other nodes 3c and 3d accommodating the terminal devices 7c and 7d via the d and DIUs 5c and 5d have substantially the same configuration as in FIG. Also, the node 3a on the trunk LAN 1 has almost the same configuration as each of the above-mentioned nodes, but in particular, the DSTI 4a, DIU 5
A multi-drop host device 6 is connected via a.

In the configuration of the node 3b shown in FIG.
0b is a basic node unit, 11b is a trunk LAN1 and DSTI
4b, CX-MAC as an interface with 100, 100
b is the CPU of the CX-MAC 11b, 101b is the CX-M
AC11b network clock I / F section, 102b is CX-M
AC11b speech path I / F unit, 103b is CX-MAC
11b is a DSTI I / F unit. In implementing the multi-drop communication control method of the present invention, it is not necessary to use the network clock I / F unit 101b in the above configuration.

Next, FIG. 2 conceptually shows a functional structure for explaining a control process for upstream data communication inside the CX-MAC 11b. In the figure, 2
00b is a transmission buffer for temporarily storing the transmission data from the DIUs 5b-1 to 5b-n, and 201b is a transmission buffer 20.
The transmission data within 0b is the frame 202b of the trunk LAN1.
Control table (transmission MAP) for placing on the vehicle, 203b
Is a reception buffer that temporarily stores the data received from the frame 202b on the trunk LAN 1 before transmitting the data to the DIUs 5b-1 to 5b-n, and 204b is a control table for loading the reception data on the reception buffer 203b (reception MAP). The figure shows CX-MAC.
Since it is a conceptual diagram related to the internal functional structure of 11b, the CX-
Illustration of the DSTI 4b interposed between the MAC 11b and the DIUs 5b-1 to 5b-n is omitted.

In the CX-MAC 11b having such a configuration, the DIU 5 of each area on the reception MAP 204b is
The area to which any of b-1 to 5b-n is connected is always set. CPU1 of CX-MAC11b
In 00b, the data received from the frame 202b on the trunk LAN 1 through the set area is stored in the reception buffer 203b, and DIUs 5b-1 to 5b- are stored.
Control to transmit to each of n.

On the other hand, DIUs 5b-1 to 5b-n
The transmission of data to the frame 202b on the trunk LAN 1 is realized by the control as described below in the CPU 100b of the CX-MAC 11b. In the control described below, in particular, two DIUs respectively accommodating the terminal devices 7b-1 and 7b-2 with respect to the DSTI 4b.
Consider a configuration in which (5b-1, 5b-2) are connected.

For example, when the terminal device 7b-2 which receives the data from the host device 6 returns a response to the host device 6, the terminal device 7b-2 first turns on the RS line, and then the DIU 5b-2 The transmission of the data frame is started by recognizing that the RS line is turned on. The DIU 5b-2 is in the mark state until the transmission of this data frame is started, and is all in the state of "1".

When the transmission of the data frame is started from the DIU 5b-2, the data is transferred via the DSTI 4b (not shown in FIG. 2) to the buffer corresponding to the DIU 5b-2 in the transmission buffer 200b of the CX-MAC 11b. It is stored in the area in units of 8 bits (1 byte).

At this time, in the CX-MAC 11b, the CPU
100b searches the contents of the transmission buffer 200b and constantly monitors whether or not data is stored in each buffer area of the transmission buffer 200b.

When the data frame has not arrived from the DIU, the transmission buffer 200b is in the mark state, and therefore "FFh" is stored in the HEX code display as the content of the buffer area corresponding to the DIU (for example, FIG. 2). Buffer area corresponding to DIU 5b-1). At this time,
The CPU 100b of the CX-MAC 11b sets (that is, resets) "00" on the transmission MAP 201b corresponding to the buffer area, and stops the transmission of data from the transmission buffer 200b to the frame 202b on the trunk LAN 1.

On the other hand, when data arrives at the start of transmission of a data frame from the DIU 5b-2, a value other than "FFh" (x in this example) is stored in the buffer area of the transmission buffer 200b corresponding to the DIU 5b-2. Is stored. Here, since a method of inserting 1 bit of "0" next when "1" continues for 5 bits or more is adopted in the data frame from the DIU 5b-2, the corresponding data in the transmission buffer 200b is received during the reception of the data frame. “FFh” is not stored in the buffer area.

When the CPU 100b of the CX-MAC 11b detects a value (x) other than "FFh" in the buffer area corresponding to the DIU 5b-2 of the transmission buffer 200b, the transmission MAP 201b corresponding to the buffer area concerned.
Is set, and the value (x) of the data frame from the DIU 5b-2 is placed on the frame 202b on the trunk LAN 1 and transmitted.

After that, the terminal device 7b-2 sets the RS line to OF
When set to F, DIU 5b-2 stops transmitting data frames. At this time, the value of the data stored in the transmission buffer 200b corresponding to the DIU 5b-2 becomes "FFh", so that the CPU 100b of the CX-MAC 11b transmits M.
The AP 201b is reset, and data transmission to the frame 202b on the trunk LAN 1 is stopped.

The above processing operation is performed when the terminal device 7b-2 connected to the node 3b of the trunk LAN 1 via the DSTI 4b and DU 5b-2 transmits the upstream data in response to the data reception from the host device 6. As an example, the other terminals 7c and 7d that are similarly connected to the nodes 3c and 3d of the trunk LAN 1 also perform the same processing regarding the upstream data transmission to the host device 6.

The processing operation of the CX-MAC software relating to the communication control system of the present invention described above is summarized in FIG.
It is shown in the flowchart. According to this processing operation, a plurality of DIUs are connected to the DSTI, a transmission buffer corresponding to each DIU is provided inside the CX-MAC, and the contents of the transmission buffer are searched in order. Describes how to proceed with communication control.

First, in the CX-MAC CPU, an initial value n = 1 is set as a set value for retrieving the n-th DIU among the plurality (S301). Next, the CPU searches whether or not the transmission buffer of the first DIU corresponding to the set value (n = 1) is FFh (S30).
2).

Here, if the content of the transmission buffer is other than FFh (NO in S302), the CPU turns on the transmission MAP corresponding to the transmission buffer (S303), and sets the content of the transmission buffer into a frame of the trunk LAN. Send and send.

On the other hand, the contents of the transmission buffer are FF.
If it is h (YES in S302), then the CPU turns off the transmission MAP corresponding to the transmission buffer (S30).
4) Stop transmission of the contents of the transmission buffer.

When the processing of S303 or S304 is completed, the CPU next sets the set value for DIU search to 1
After adding (S305), it is determined whether or not the number of DIUs for searching has reached a prescribed number (S306).

Here, while the set number has not been reached (S30
6NO), the CPU repeatedly executes the processing of S302 and subsequent steps, and continues the subsequent search of the data in the transmission buffer regarding the DIU and the control of data transmission or transmission stop based on the search result.

By continuing the above processing until the number of DIU searches reaches the specified number (YES in S306), when there are data in the transmission buffers corresponding to a plurality of DIUs, the data is transmitted to the frame of the trunk LAN. The communication control peculiar to the method of the present invention is possible in which the transmission is stopped when there is no data. According to the control method of the present invention, a control path for transmitting and receiving a control command for securing a communication path is not necessary in addition to the communication path at the time of upstream data communication, and is used in the conventional circuit when configuring the CX-MAC. The control path I / F unit 104b (see FIG. 5) can be removed.

[0040]

As described above, according to the present invention,
DIU C data frame only when RS line is ON
The data is transmitted to the X-MAC, the CX-MAC constantly searches the transmission buffer, and while the data is detected in the transmission buffer, the transmission MAP is set to transmit the data in the transmission buffer to the trunk LAN, and When no data is detected in the transmission buffer, the transmission MAP is reset to stop the data transmission to the trunk LAN. Therefore, during uplink data communication, control commands for transmitting and receiving a communication path separate from the communication path are sent and received. A control path for
CX-MAC without I / F related to control of this control path
By using, there is an advantage that the circuit structure and the control process can be simplified at the same time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a node in a data communication system to which a multi-drop communication control system of the present invention is applied.

2 is a conceptual diagram showing a functional structure of CX-MAC in the node shown in FIG.

3 is a flowchart showing an example of a multi-drop communication control operation by CX-MAC in the node shown in FIG.

FIG. 4 is a general system configuration diagram of a data communication system to which this type of multi-drop communication control system can be applied.

FIG. 5 is a block diagram showing a configuration of a node in a data communication system to which a conventional multi-drop communication control system is applied.

[Explanation of symbols]

 1 main line LAN 2 transmission line 3a to 3d main line LAN node 4a to 4d DSTI 5a to 5d DIU 6 host device 7b to 7d terminal device 10b node basic unit 11b CX-MAC 100b CPU 101b network clock I / F unit 102b communication line I / F unit 103b I / F unit for DSTI 104b Control path I / F unit 200b Transmission buffer 201b Transmission MAP 202b Frame on main line LAN 203b Reception buffer 204b Reception MAP

Claims (3)

[Claims] 1. A multi-drop host device is connected to one node of a trunk LAN via a terminal interface and a data interface unit, and other nodes of the trunk LAN are similarly connected to a terminal interface,
In a data communication system comprising one or a plurality of multi-drop terminal devices connected via a data interface unit and performing one-to-n communication between the host device and each of the terminal devices, each node includes each of the terminals. A transmission buffer for temporarily storing the data received from the data interface unit of the device, and a transmission M for putting the contents of the transmission buffer into a certain time slot on the frame of the trunk LAN.
The data in the transmission buffer, which is provided with at least an AP, is constantly searched for whether or not the response data transmitted from each terminal device in response to the reception of the inquiry data from the host device exists in the transmission buffer. Is set, the transmission MAP is set to transmit the data to the trunk LAN, and when there is no data in the transmission buffer, the transmission MAP is reset to stop the data transmission to the trunk LAN. A multi-drop communication control method characterized by controlling. 2. The data interface unit turns on / off a transmission request line of a terminal device connected to the own unit.
2. The multi-drop communication control system according to claim 1, wherein F is detected, and transmission / transmission stop control of response data from the terminal device to the corresponding node is performed according to the detection result. 3. The interface unit is a CCITT
Recommendation V. 24 / V. 3. The multi-drop communication control system according to claim 1, wherein the multi-drop communication control system is configured by an interface means capable of supporting data communication by 28.