JP2000010682A - Bus system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bus system capable of appropriately increasing or reducing the number of substrates as necessary. SOLUTION: This bus system is provided with backboards 1a, 1b and 1c for addition provided with a socket 3 for mounting the substrate 21, connectors 4 for being connected to each other and a substrate detection switch 5 for detecting the presence/absence of the mounted substrate and a terminating resistance control board 10. Thus, the number of the substrates 21 connected to the connector 4 of the backboard for the addition and mounted is judged by signals from the substrate detection switch 5 and a required terminating resistance value is set.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus system which is a signal wiring used for exchanging signals between a plurality of boards in a control box, a control panel, and the like. A bus system that can be performed.

[0002]

2. Description of the Related Art A bus system is used to secure wiring for signals exchanged between a plurality of boards provided inside a control box or a control panel (this is called a bus line). It is.

Conventionally, in such a bus system, a back board provided with a plurality of sockets for mounting a board in advance inside a control box or a control panel is prepared, and the back board is inserted into the socket. A bus line for exchanging signals between the mounted boards is built in, and the boards themselves can receive necessary signals and supply power simply by being inserted into a socket of the backboard.

[0004]

In such a conventional bus system, the number of sockets provided on the backboard, that is, the number of boards that can be mounted is predetermined. Specifically, for example, the number of sockets is determined by the backboard such as four, eight, or sixteen, and there is a problem that it is not possible to add a board that exceeds the number later. . Also, in order to be able to increase the number of boards later, a backboard provided with a larger number of sockets than initially used may be used. If there is a possibility that the number of sockets will be increased, but it is not clear whether the number of sockets will be increased to fill all the sockets, a large backboard with more sockets than the number of boards actually used will be used. Therefore, the control box and the control panel themselves are unnecessarily increased in size, and the installation space is increased, which is not preferable.

Accordingly, an object of the present invention is to provide a bus system capable of appropriately increasing or decreasing the number of boards as required.

[0006]

The object of the present invention is achieved by the following means.

(1) A bus system capable of increasing or decreasing a plurality of boards as required, wherein at least one socket for mounting the boards, a connector for connecting to each other, and the presence or absence of the board mounting And an extension backboard having a board detection switch for detecting the connection, and a connector connected to the connector provided on the extension backboard and mounted by a signal from the board detection switch provided on the extension backboard. A termination resistance control board having control means for setting a required termination resistance value by judging the number of boards to be set.

(2) The control means includes a plurality of resistors and a switching circuit, and the switching circuit controls the plurality of resistors according to a state of the board detection switch provided on the additional backboard. The terminal resistance is set in accordance with the number of mounted boards by switching the connections of the above.

(3) The signal from the board detection switch provided in the extension backboard is independent of the control means when there are a plurality of extension backboards. It is characterized by being input to.

(4) The extension backboard includes a signal line for guiding a signal from the board detection switch provided in the extension backboard to the control means in the termination resistance control board. The present invention is characterized in that a plurality of boards are provided in accordance with a predetermined number of expandable boards, and the signal lines used in each of the additional backboards are set by signal line selection switches.

[0011]

According to the present invention configured as described above, the following effects can be obtained for each claim.

According to the first aspect of the present invention, the extension backboard has at least one socket for mounting a board, a connector for connecting the extension backboards to each other, and the extension backboard. A board detection switch for detecting whether the board is mounted on the socket of the board; and a board mounted on the termination resistance control board by a signal from the board detection switch provided on the extension backboard. Control means for detecting the number of terminations and setting the terminating resistance value according to the number of boards is provided, and a bus system is formed by these additional backboard and terminating resistance control board. The number of boards can be easily increased or decreased by appropriately increasing or decreasing the number of additional backboards. Since the terminal resistance value becomes is automatically set, the setting of the termination resistance associated with the increase or decrease of the substrate becomes unnecessary, it is possible to very easily increase or decrease of the substrate.

According to the second aspect of the present invention, the connection of the plurality of resistors is switched according to the number of boards mounted by the switching circuit, so that the connection is increased by a simple combination of the switch circuit and the resistors. The termination resistance value according to the number of boards is automatically set in accordance with the state of the board detection switch provided on the backboard.

According to the third aspect of the present invention, the signal from the board detection switch provided on the additional backboard is input independently to the control means on the termination resistance control board. For example, when there are a plurality of extension backboards themselves, even when the boards are not mounted in some of the extension backboard sockets, the number of boards actually mounted is The appropriate setting of the terminating resistance value can be performed reliably.

According to the fourth aspect of the present invention, signal lines for guiding signals from the board detection switches in the additional backboard are provided and used by a predetermined number of addable boards. Since the signal line is set by the signal line selection switch on each extension backboard, the signal from the board detection switch provided on each extension backboard is independently set by setting the signal line selection switch. Since the control means can be guided, all the extension backboards can be manufactured in the same form regardless of the connection order and the positional relationship of the extension backboards.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

FIG. 1 is a perspective view showing one additional backboard used in the bus system of the present invention, FIG. 2 is a perspective view showing the same terminating resistance control board, and FIG. FIG. 3 is a diagram showing a state in which a bus system is constructed by combining a backboard for use with a termination resistance control board.

As shown in FIG. 1, the extension backboard 1 includes a backboard substrate 2 and the backboard substrate 2.
A socket 3 for inserting a board provided as an application (hereinafter referred to as an application board) to secure a signal line between the socket and the application board;
Another extension backboard or a terminating resistance control board to be described later is inserted, a connector 4 for connecting bus line paths to each other, and an application board is inserted inside the socket 3 when the application board is inserted. And a micro switch 5 for detecting that the operation has been performed. Wiring for bus lines is formed on the backboard substrate 2 of the additional backboard 1, and when a plurality of the additional backboards 1 are connected as shown in FIG. A bus line is formed. The wiring for the bus lines formed on the backboard substrate 2 is the same as the wiring for the bus lines formed on the conventional backboard, and is not shown.

As shown in FIG. 2, the terminating resistance control board 10 includes a terminating resistance control board substrate 12 and a decoder IC 13 for detecting the on / off state of the microswitch 5 in the extension backboard 1. A plurality of resistors 15 necessary for setting the terminating resistance value, and a switching IC 14 for switching a combination of the plurality of resistors 15 according to a signal from the decoder IC 13 such that the terminating resistance value corresponds to the number of substrates. . The direction of the arrow in the figure is the direction of insertion into the connector 4 of the additional backboard 1.

In the bus system using the extension backboard 1 and the terminating resistance control board 10, as shown in FIG. 3, a plurality of extension backboards 1 are continuously connected by a connector 4 (this embodiment). Then, in order to distinguish each extension backboard, the terminating resistance control board 10 is connected to the connector 4 of the terminating extension backboard 1c in order to distinguish each extension backboard 1a, 1b, and 1c. It will be.

In the bus system thus constructed, the application boards 21, 22, and 23 are inserted into the sockets 3 of the respective extension backboards 1, and the signals of the respective application boards are transmitted to each other in the extension backboard 1. It is exchanged through the bus line. Further, the bus system constructed in this way is connected to a main controller such as a control box or a control panel (the extension backboard 1a is connected to a connector provided in the main controller or the like), and the extension is performed. Signals are exchanged through bus lines formed on the backboard 1, and power is supplied.

The application boards 21, 22,
As the 23, there are various types such as a substrate in which circuits for controlling various machines and devices are incorporated, and a memory substrate simply for increasing the storage capacity.

Here, a terminating resistor in such a bus system will be described.

The role of the terminating resistor is mainly to match the impedance of the bus line, and the total length of the wiring in the application board and the bus line depends on the number of application boards used. If the resistance value of this terminating resistor is not set to an appropriate value according to the number of boards, unnecessary reflection of the signal will occur at the end point of the bus line. This is to prevent it. For application boards used in bus systems that use such boards properly inserted, the impedance of each board has been conventionally standardized in the usual case.
The impedance of each application board is a constant value. Therefore, the required value of the terminating resistor becomes a specific value according to the number of application boards, for example, 270Ω when two application boards are used, and 330Ω when three application boards are used.

In the present embodiment, the terminating resistance control board 10 automatically sets the terminating resistance value according to the number of mounted boards.

FIG. 4 is a block diagram showing a circuit configuration for controlling a terminating resistance value in a bus system including three additional backboards 1 and a terminating resistance control board 10.

As shown in FIG. 4, the signal from the microswitch 5 provided on each additional backboard 1 is
The signal is input to the decoder IC 13 in the termination resistance control board 10 via the independent signal lines 51. In the decoder IC 13, the input microswitch 5
And how many application boards are connected. In this case, for example, an independent signal from each microswitch 5 is received, and the signal is inserted based on the number of ONs of each signal (assuming that the application board is inserted when the microswitch is ON). Determine the number of application boards.

Then, based on the result of this determination, a switch switching signal is output to the switching IC 14 in order to switch the connection relationship between the plurality of resistors 15. The switching IC 14 switches the connection relationship of the plurality of resistors 15 based on the input signal. In the case shown,
When one application board is used, one resistor is switched between ground and the bus line 31. When two application boards are used, two resistors are inserted between ground and the ground. The connection relation of the resistors is similarly switched when there are a plurality of application boards. This allows
The value of the terminating resistance of the bus line 31 passing through each extension backboard 1 is switched according to the number of application boards.

The switching ICs 14 for switching the terminating resistors and the plurality of resistors 15 need to be provided with terminating resistors for each of the plurality of bus lines 31.

The signals from the microswitch 5 are input to the decoder IC 13 independently of each other. For this reason, each extension backboard 1 is provided with the same number of signal lines for micro switches as the limit number of extension switches, which will be described later, and further to determine which of these signal lines for micro switches to use. Each extension backboard 1 is provided with a dip switch (not shown) for switching a signal from the microswitch to a plurality of microswitch signal lines. When a plurality of extension backboards 1 are connected, the DIP switches are switched so that the signals from the microswitches 5 of the extension backboards 1 are set independently so as not to overlap each other. Thus, even if the additional backboards 1 are made exactly the same, they can be used at any position regardless of the connection relationship.

By independently detecting the signals from the microswitches 5 in this manner, for example, when the application board is temporarily removed, that is, as shown in FIG. Even when the application board 21 is mounted only on one extension backboard 1a and the sockets of the other extension backboards 1b and 1c remain empty, the number of boards actually used is (One in the case shown in FIG. 4), the optimum termination resistance value is set. Of course, as shown in FIG. 3, when the application boards are mounted on all three additional backboards, the switching is performed so that the termination resistance values correspond to the three application boards.

Here, the limit of the number of application boards that can be added in this embodiment will be described.

As described above, the bus system according to the present embodiment is capable of adding necessary application boards by sequentially connecting additional backboards. However, the number of added boards is infinite. It cannot be expanded and has certain limitations. This limit is determined by the signal attenuation characteristics of the bus line. The signal attenuation characteristics are determined by the voltage and signal frequency to be used and the characteristics of the wiring used for the bus line (resistance of the wiring itself, inductance of the bus line, etc.). If the total length of the internal wiring and bus lines is long, the signal will be attenuated in accordance with the signal attenuation characteristics. Therefore, the maximum number of addable units is determined by the signal attenuation characteristics. For example, when the characteristics of the wiring used for the bus line are the same at the same signal frequency, when the voltage is low, the limit number of expandable units is reduced, and when the voltage is high, the number of expandable units can be increased. The signal frequency and wiring characteristics may vary depending on the application board used.
In the normal case, the frequency band to be used and the characteristics of the wiring are determined in advance from the signal attenuation characteristics. Therefore, the expansion limit of the bus system according to the present embodiment is limited by the control box or control panel using the signal. Will be determined in advance depending on the voltage used for

Therefore, the number of wirings for the microswitches in the extension backboard 1, the number of switches of the switching IC 14 in the termination resistance control board 10, and the number of the resistors 15 are determined by the signal attenuation characteristics of the bus lines. It is preferable to make the number equal to the possible limit number. However, it is not always necessary to match the limit of the number of addable boards. For example, when the limit of the number of addable boards is 100, the number of application boards actually used may be increased to about 20 in any way. In such a case, the number of application boards that can be added is determined in advance to be 20, and the number of signal lines 51 in the additional back board 1 and the terminating resistance control board The number of switches and the number of resistors of the switching IC in 10 may be determined. By previously setting the number of application boards that can be added irrespective of the signal attenuation characteristics of the bus lines, the number of components such as ICs and resistors to be used can be reduced.

In the bus system of the present embodiment described above, when it is desired to add an application board, the additional back board 1 is continuously connected to the connector 4,
By connecting the terminating resistance control board 10 to the connector 4 of the last extension backboard 1, the number of application boards can be appropriately increased until the extension limit is reached, and the terminating resistance according to the number of application boards is automatically adjusted. Is set to For this reason, in the initial stage, if the additional backboards 1 are connected by the number actually used, no wasted space is taken up. Since it is only necessary to add an additional backboard according to the situation, as in the past, if you use a backboard that has more sockets than necessary in advance, or if you replace the entire backboard because the number of sockets is insufficient, It is no longer said that the application boards can be easily added.

In the above-described extension backboard, one socket is shown. However, the present invention is not limited to this. For example, two or three sockets may be provided on one backboard substrate. Boards may be prepared and used according to the number of additional application boards. For example, to add one application board, connect an extension backboard provided with one socket, and to add two application boards, use an extension backboard with two sockets. I do.

Although the embodiment of the present invention has been described above, the present invention is not limited to such an embodiment, and it goes without saying that those skilled in the art can appropriately modify the present invention within the technical idea of the present invention. No.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an additional backboard used in an embodiment to which the present invention is applied.

FIG. 2 is a perspective view showing a termination resistance control board used in an embodiment to which the present invention is applied.

FIG. 3 is a diagram showing a state in which a bus system according to an embodiment to which the present invention is applied is assembled.

FIG. 4 is a block diagram for explaining a circuit configuration for controlling a terminating resistance in the bus system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Expansion board, 2 ... Backboard board, 3 ... Socket, 4 ... Connector, 10 ... Terminating resistance control board, 12 ... Terminating resistance control board board, 13 ... Decoder IC, 14 ... Switching IC, 15 ... Resistor .

Claims (4)

[Claims] 1. A bus system capable of increasing or decreasing a plurality of boards as needed, wherein at least one socket for mounting the boards is provided.
A connector for connecting to each other, and an extension backboard having a board detection switch for detecting whether or not the board is mounted; and an extension backboard connected to the connector provided on the extension backboard, A bus system comprising: a termination resistance control board having control means for judging the number of mounted boards based on a signal from the board detection switch provided and setting a required termination resistance value. . 2. The control means comprises a plurality of resistors and a switching circuit, and the switching circuit controls the plurality of resistors according to a state of the board detection switch provided on the additional backboard. 2. The bus system according to claim 1, wherein the connection is switched to set a terminating resistance value corresponding to the number of mounted boards. 3. A signal from the board detection switch provided in the additional backboard, when there are a plurality of additional backboards, the signal is sent to the control means independently from each of the additional backboards. 3. The bus system according to claim 1, wherein the bus system is inputted. 4. The extension backboard includes a signal line for guiding a signal from the board detection switch provided in the extension backboard to the control means in the termination resistance control board in advance. 4. The bus system according to claim 3, wherein a number corresponding to the determined number of extendable boards is provided, and the signal lines used in each extension backboard are set by signal line selection switches.