JPH0715446A - Communication control system - Google Patents

Abstract

(57) [Summary] [Purpose] With a simple configuration, avoiding unnecessary failure display and unnecessary fail-safe operation when the option unit is not connected, without increasing the device cost. To [Structure] For connection judgment of an option unit that has a built-in resistor with a resistance value that is different from each other and does not match the combined resistance value of the communication line terminals to which the option unit is not connected The cap B103 or the optional unit connection determination cap C104 is attached and grounded, and the transition of the current value flowing through the communication line of the management unit 101 is detected to determine the presence or absence of the optional unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication control system for controlling communication of a local area network (LAN) to which a management unit (master station) and a plurality of job units (slave stations) can be connected.

[0002]

2. Description of the Related Art As a conventional communication control system, for example, there is a communication control system for controlling communication of a local area network (LAN) to which a management unit (master station) and a plurality of job units (slave stations) can be connected. Generally, in such a communication control system, the management unit outputs a signal SM (transmission command signal) to each job unit, and the job unit receiving the signal SM performs a transmission operation.

When an abnormality occurs in the operation of any of the job units, the management unit detects the abnormality and commands the other job units except the abnormal unit to perform the transmission operation. The driver is notified of the abnormality via a predetermined failure display means. Here, when the management unit detects an abnormality, for example, when a signal indicating the abnormality is received from the abnormality unit itself, or the signal S from the management unit is received.
An error in the job unit is detected when the job unit does not respond to M correctly. An example of such a communication control system is a mobile multiplex communication device mounted on a vehicle or the like.

On the other hand, in vehicles such as automobiles, various sub-functions are optional settings, and in many cases, customers can freely select them. Therefore, in such a case, the number and types of option units (that is, job units) connected to the local area network differ according to the option setting. Also,
After purchasing the vehicle, an optional unit may be purchased separately at a dealer or the like and connected. However, it goes without saying that the management unit is always connected regardless of the presence or absence of the option unit.

[0005]

However, when the above-mentioned conventional communication control system is installed in a vehicle, an abnormality is detected when the option unit does not correctly respond to the signal SM from the management unit. Even when the option unit is not connected, it is determined that the option unit is out of order, and there is a possibility that unnecessary failure display or unnecessary fail-safe operation may be executed.

Further, in order to prevent unnecessary failure display and unnecessary fail-safe operation, it suffices not to execute communication with an optional unit that does not exist. Since a means to set (or input) the presence or absence in advance is required,
There were problems that the device configuration became complicated and that the device cost increased. Alternatively, a method of simply replacing a part of the management unit can be considered, but there is a problem in that the device configuration is similarly complicated in terms of changing the management unit and a device cost is increased.

The present invention has been made in view of the above, and has a simple structure without increasing the device cost.
The purpose is to prevent unnecessary failure display and execution of unnecessary fail-safe operation when the option unit is not connected.

[0008]

In order to achieve the above object, the present invention provides communication control of a local area network (LAN) to which a management unit (master station) and a plurality of job units (slave stations) can be connected. In the communication control system, the communication line terminals to which the job unit is not connected among the communication line terminals of the local area network have different resistance values for each job unit and match with a value obtained by combining other resistance values. (EN) A communication control system provided with a communication line terminal grounding means for grounding via a resistor having a resistance value.

In order to achieve the above object, the present invention, in addition to the above-mentioned configuration, applies a voltage to a communication line after power is turned on, and based on the transition of the current value flowing at that time,
It is intended to provide a communication control system including a job unit connection discriminating means for discriminating unconnected job units.

Further, in order to achieve the above object, the present invention, in addition to the above-described configuration, makes a job unit not subject to communication control and failure diagnosis when it is determined that it is not connected. The present invention provides a communication control system including a job unit non-connection control means.

[0011]

In the communication control system of the present invention, the communication line terminal grounding means is attached to the communication line terminal to which the job unit is not connected, and the resistance value is different for each job unit and the other resistance values are combined with each other. Ground through a resistor with a resistance that does not match the value to clarify that the job unit is not connected.

Further, the job unit connection determining means applies a voltage to the communication line after the power is turned on, and determines the unconnected job units based on the transition of the current value flowing at that time.

Further, the job unit non-connection control means excludes the corresponding job unit from the targets of communication control and failure diagnosis.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the communication control system of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention.
In the present embodiment, three job units can be selectively connected as optional units, and here, an example is shown in which one job unit is connected as an optional unit A.

In the figure, 101 is a management unit (master station) connected to a local area network (LAN), which is permanently installed. The management unit 101 includes a microprocessor 101a,
It is composed of a communication control IC 101b, an option discrimination transmission line switching circuit 101c, and a current detection circuit 101d. Here, the microprocessor 101a mainly transfers and controls the data to and from the communication control IC 101b, but also executes the connection status determination of the option unit at the time of initialization immediately after the power is turned on. Microprocessor 101a and communication control IC
Both 101b transfer data via the address bus and the data bus. The transmission line switching circuit 101c for option discrimination is a transmission terminal of the communication control IC 101b,
Either the reference voltage or GND is used for the communication line (that is, LA
N), which is switched and connected, and operates by the output of the microprocessor 101a. Current detection circuit 10
1d is a circuit for differentially amplifying the voltage generated in the shunt resistor, for example. Further, in order to improve the reliability against GND floating and noise in the communication control system, as shown in the figure, the communication line is provided with a capacitor C0 and a resistor R.
0 is inserted for capacitor coupling.

Reference numeral 102 is an option unit A that is actually connected. The option unit A102 includes a microprocessor 102a and a communication control IC 102b. The microprocessor 102a transfers data to and controls the communication control IC 102b. Further, in order to improve the reliability against the GND floating and noise in the communication control system, as shown in the figure,
A capacitor C0 and a resistor R0 are inserted in the communication line for capacitor coupling.

Reference numerals 103 and 104 denote option unit connection discriminating caps B and C which are communication line terminal grounding means connected to a communication line terminal to which an option unit is not connected. The optional unit connection determination cap B103 and the optional unit connection determination cap C104 are, as shown in the figure, a capacitor C0 having a predetermined capacitance and resistors Rb and Rc having a predetermined resistance value connected in series, and a resistor Rb. , Rc is grounded via one end.

FIG. 2 shows a specific structure of the optional unit connection determination cap B103 and the optional unit connection determination cap C104.
Between the terminals 202 and 203 of 01, the capacitor C0 having the above-mentioned predetermined capacitance and the resistor Rb having the predetermined resistance value,
Rc is connected in series, and the entire circuit is grounded via a terminal 203.

The operation of the above configuration will be described. When the communication control system is powered on, the management unit 101 starts the operation of the option unit connection determination job. This option unit connection discrimination job is a routine executed by the microprocessor 101a every 10 msec. First, the transmission terminal of the communication control IC 101b is fixed to the GND level by the option discrimination transmission line switching circuit 101c for a certain period of time. Each capacitor C0 installed in the communication line by
Initialize the electric charge accumulated in the circuit, then apply the reference voltage level Vcc to the transmission terminal by the option discriminating transmission line switching circuit 101c, measure the current value at that time (current value I described later), and Current is passed from the management unit 101 to each capacitor C0 until the capacitor C0 is saturated and is in a steady state. At least during this period, if the transmission function of the option unit is disabled, the communication control IC 101 in the management unit 101
All of the receiving terminal and the transmitting terminal of b are in a high impedance state, so that the inflow and outflow of current can be prevented.

Therefore, even in the communication control system of this embodiment shown in FIG. 1, it is sufficient to pay attention only to the partial circuit shown in FIG. Management unit 1
The current value flowing out from the transmission terminal 01 is the reception terminal of the management unit, the reception terminal of the option unit A102, and the cap B10 for discriminating the connection of the option unit.
3, and optional unit connection discrimination cap C1
04 is the sum of the current values flowing into the capacitors C0 incorporated in each. For example, in the connection state of Fig. 1,
As shown in FIG. 3, the current value flowing from the transmitting terminal of the management unit 101 is I, the current value flowing into the capacitor C0 of the receiving terminal of the management unit 101 is I ₁ , and the current value flowing into the capacitor C0 of the receiving terminal of the option unit A102. Let I _{2 be} the current value flowing into the capacitor C0 of the cap B103 for discriminating the connection of the option unit to I ₃ , and the current value flowing into the capacitor C0 of the cap C104 for discriminating the connection of the option unit to be I ₄ .

I = I ₁ + I ₂ + I ₃ + I ₄ = 2 / R 0 (1-exp (−2t / C0 · R0)) Vcc + 2 / R0 (1-exp (−2t / C0 · R0)) Vcc + 1 / Rb (1-exp (-t / C0.Rb)) Vcc + 1 / Rc (1-exp (-t / C0.Rc)) Vcc However, the values of resistors R0, Rb, and Rc can be arbitrarily combined. Is set in advance so that the sum does not match. For example, the following resistance values can be set.

Dividing resistor for receiving circuit of the connected option unit R0 = 11 kΩ Resistance of cap B103 for discriminating connection of option unit Rb = 3 kΩ Resistance of cap C104 for discriminating connection of option unit
Rc = 7 kΩ In this embodiment, the case where the option unit A102 is connected as shown in FIG. 1 is taken as an example. However, when the option unit connection determination cap is attached without connecting the option unit A102. For example, if this resistance value is Ra, Ra = 2k
You can set it to Ω.

In this case, as shown in the current characteristic by the relationship between the current I and the time t in FIG.
In the case of no connection, without option unit B, without option unit C, without option units A and B, without option units A and C, and with any connection combination without option units B and C However, their current characteristics do not match each other. Therefore, by storing those characteristics in a memory (not shown) in the microprocessor 101a of the management unit 101 in advance and comparing with the current value I detected by the current detection circuit 101d, which option unit is connected. Can determine whether or not. However, optional units B and C
Is the cap B for discriminating the connection of the optional unit.
103 and optional unit connection determination cap C
An optional unit connectable to the position 104 is shown.

In the case of the present embodiment, if the current detecting shunt resistance of the current detecting circuit 101d is set to about 100Ω, the influence on the current characteristic of FIG. 4 becomes small, and if the voltage drop is measured, It is possible to detect current.

If the connection information of this option unit is present, it is possible to distinguish between the connected option unit and the unconnected option unit, and no signal is transmitted to the unconnected option unit.
The signal processing speed of the management unit 101 is increased. Further, it is needless to say that accurate failure determination can be performed when the failure determination of the option unit is performed using a known method.

FIG. 5 shows a microprocessor 101a
The specific flowchart of the option unit connection determination job executed every 0 msec is shown.

In step S501, a connection determination end flag indicating whether or not the connection determination is completed is checked,
If it is "0" (1: end, 0: connection determination is not executed), the process proceeds to step S502. If it is not "0", this routine is ended.

In step S502, the initialization operation end flag indicating whether or not the initialization operation has been completed is checked. If "1" (1: end, 0: initialization processing not executed), go to step S507. If it is not "1", the process proceeds to step S503.

In step S503, the communication control IC 1
The option determining transmission line switching circuit 101c is instructed to fix the transmission terminal of 01b to the GND level.

In step S504, the timer T1 is incremented. However, it is assumed that the timer T1 is initialized to the timer value "0" in advance before the execution of this routine.

In step S505, it is determined whether the timer T1 has exceeded the predetermined time Tint, and T1> Tint.
If so, the process proceeds to step S506, and if T1> Tint is not satisfied, this routine ends.

In step S506, the initialization operation end flag is set to "1".

In step S507, the communication control IC 1
The option discriminating transmission line switching circuit 101c is instructed to fix the transmission terminal of 01b to the reference voltage level (Vcc).

In step S508, the peak current I _peak flowing out from the transmission terminal is measured. In step S509, the peak current I _peak is compared with various data stored in advance (current characteristics in FIG. 4) to determine the presence / absence of an unconnected option unit.

In step S510, "1" is set to the connection determination end flag.

As described above, in the present embodiment, the communication line terminals to which the job unit is not connected, such as the optional unit connection determination cap B103 and the optional unit connection determination cap C104, have a resistance having a predetermined resistance value. It is grounded via, and the transition of the current value flowing in the communication line of the management unit 101 is detected to determine the presence or absence of the option unit.
It is possible to avoid unnecessary failure display and execution of unnecessary fail-safe operation when the option unit is not connected, without increasing the device cost. In addition, since the communication access to the non-connection option unit can be stopped, the communication speed can be optimized.

In the above-described embodiment, the maximum number of option units that can be connected is three, but the number of option units is not limited to this.
For example, the number can be increased to 7 or 10. However, the resistance value of each option unit connection determination cap must be set differently for each option unit, and the resistance values of the other units must be set in advance so that they do not match the combined value. . Further, it is needless to say that the correspondence between the resistance value of each option unit connection determination cap and the mounting terminal of each option unit must be determined in advance.

[0039]

As described above, according to the present invention,
The communication line terminal grounding means is attached to the communication line terminal to which the job unit is not connected, and a resistor having a different resistance value for each job unit and a resistance value that does not match the combination of other resistance values with each other is used. Grounded through
A voltage is applied to the communication line after the power is turned on, and the job units that are not connected are identified based on the transition of the current value that flows at that time. Therefore, with a simple configuration, optional units can be connected without increasing the device cost. It is possible to avoid unnecessary failure display and execution of unnecessary fail-safe operation when not performed. In addition, communication access to the unconnected option unit can be stopped to optimize communication at high speed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration example of an embodiment of the present invention.

FIG. 2 is a specific configuration diagram of an optional unit connection determination cap.

FIG. 3 is a circuit diagram in which parts necessary for explanation are extracted from the configuration of FIG.

FIG. 4 is a graph showing current characteristics according to the relationship between current I and time t.

FIG. 5 is a flowchart of an option unit connection determination job.

[Explanation of symbols]

101 Management Unit (Master Station) 101a Microprocessor 101b Communication Control IC 101c Option Discrimination Transmission Line Switching Circuit 101d Current Detection Circuit 102 Option Unit A 102a Microprocessor 102b Communication Control IC 103 Option Unit Connection Discrimination Cap B 104 Option Unit Connection discrimination cap C C0 Capacitor R0, Rb, Rc Resistance

Claims (3)

[Claims] 1. A communication control system for controlling communication of a local area network (LAN), wherein a management unit (master station) and a plurality of job units (slave stations) can be connected, in a communication line terminal of the local area network. The communication line terminals to which job units are not connected have different resistance values for each job unit,
A communication control system, further comprising communication line terminal grounding means for grounding via a resistor having a resistance value that does not match a combined value of other resistance values. 2. A voltage is applied to the communication line after the power is turned on,
2. The communication control system according to claim 1, further comprising a job unit connection discriminating means for discriminating a job unit that is not connected based on a transition of a current value flowing at that time. 3. A non-connected job unit control means for excluding the job unit from communication control and failure diagnosis when it is determined that the job unit is not connected. 1. The communication control system according to 1.