JP2001169314A - Transmission interface device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the reliability of a transmission interface device. SOLUTION: The transmission interface device is provided with a board that is a part of a system when inserted and disconnected from the system when removed and 1st and 2nd signal balanced lines that interconnect the board and the system, and intervenes the system and the board. The transmission interface device is provided with an insertion removal detection means that detects insertion or removal of the board, a signal reception means that is placed on the board and is provide with at least two input terminals connected to the 1st and 2nd signal lines, and a connection selection means that simultaneously disconnects each input terminal from the 1st and 2nd signal lines and applies a prescribed level to each input terminal respectively when the insertion removal detection means detects the removal of the board and stops application of the prescribed to each input terminal and connects the 1st and 2nd signal lines to each input terminal at the same time when the insertion removal detection means detects the insertion of the board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission interface device, and more particularly, to a transmission interface device having a bookshelf-type structure having a backplane board, such as an exchange or a transmission device, which is suitably applied to a system for performing active insertion and removal. It is something.

[0002]

2. Description of the Related Art A conventional balanced interface circuit 10 is shown in FIG. The interface circuit 10 has, for example, P
BX (private branch exchange).

In FIG. 2, a transmitting side substrate (base) PKD
1 and the receiving-side board PKR1 are connected by a backplane board (back-side connecting plate) BP1 so as to be able to be inserted and removed. The backplane substrate BP1 is a substrate provided with only wiring such as the signal line T1 for connecting the PKD1 and the PKR1.

[0004] In the case of a system such as the PBX exchange, which cannot be stopped temporarily, the insertion and removal of the transmitting side board PKD1 and the receiving side board PKR1 with respect to the backplane board BP1 are performed by energizing the entire system. This is active insertion / removal (hot-line insertion / removal) performed in an operating state.

When the transmitting-side board PKD1 is inserted into the backplane board BP1, the points b1 and b1 'and the signal line T
1 is connected to the state shown in the figure, and when it is removed, the signal line T1 and the points b1 and b1 'are disconnected, and the state shown in FIG.

Similarly, when the receiving-side board PKR1 is inserted into the backplane board BP1, the points c1 and c1 'and the signal line T1 are connected to each other, as shown in the drawing. The points c1 and c1 'are cut, and the state shown in the drawing is such that PKR1 is removed.

[0007]

The interface circuit 10 has the following problems related to hot insertion and removal.

When the transmitting-side board PKD1 is actively inserted and removed, the voltage levels of the input terminals c1 and c1 'are high level (H) or low level (L) through the signal line T1.
Is not determined, the output d of the signal receiving circuit RV1 is determined.
1 may be undefined.

When the transmitting-side board PKD1 is actively inserted and removed, noise (noise) is mixed into the signal receiving circuit RV1.
It may malfunction.

[0010] These two problems can also occur when the signal receiving side board PKR2 is hot-swapped.

However, such a problem does not always occur when the backplane board BP1 exists between the transmitting board PKD1 and the receiving board PKR1. A similar problem can occur when PKD1 and PKR1 are directly connected and separated without passing through BP1.

Regarding the latter noise, the signal line T
The length of 1 is also a factor influencing the magnitude of the influence of noise. This is because the signal line T1 functions as a receiving antenna for external noise.

[0013]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a substrate which is inserted into and becomes part of a system, which is removed and separated from the system, and a balanced connection between the substrate and the system. A transmission interface device that includes first and second signal lines and mediates signal transmission between the system and the board; (1) insertion / extraction detection means for detecting insertion or removal of the board; Signal receiving means disposed on a substrate and having at least two input terminals connected to the first and second signal lines; (3)
When the insertion / removal detection means detects removal of the board, the input terminals are simultaneously disconnected from the first and second signal lines to apply predetermined potentials, respectively, and the insertion / removal detection means detects whether the board is inserted. And connection selection means for stopping application of the predetermined potential to each of the input terminals and connecting each of the input terminals to the first and second signal lines at the same time. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION (A) Embodiment Hereinafter, a transmission interface device according to the present invention is referred to as PB
An embodiment will be described by taking as an example a case where the present invention is applied to a balanced interface circuit in an X exchange.

In this embodiment, when the board is hot-inserted and removed,
By connecting the input terminal of the receiver to the pull-up and pull-down resistors while maintaining the balance, the receiver is protected against noise and the like, and the reliability of the operation at the subsequent stage of the receiver is improved.

(A-1) Configuration of the Embodiment FIG. 1 shows a balanced interface circuit 20 of the embodiment. The balanced interface circuit 20 is a part of a system such as a private branch exchange (PBX), like the balanced interface circuit 10 described above.

A large-scale system such as a PBX switch is
An entire switching system has a structure called a bookshelf type, and the switching system includes, for example,
A board having a function as a central processing unit, a switch board having an IC for performing an exchange operation, a disk board having a disk device for performing IPL when a memory failure occurs, Between the computer terminal and the PBX exchange system, is constituted by a board having various functions such as an I / O board having an I / O device for inputting and outputting information.

The number of boards constituting one bookshelf is, for example, about 20 boards.

In the bookshelf, a board provided with signal lines for interconnecting these boards is provided as a backplane board (back connection board) BP2.
It is. The backplane substrate BP2 is a component for electrically connecting each substrate with wiring and mechanically supporting each substrate.

Therefore, the balanced interface circuit 20 as shown in FIG. 1 exists everywhere in this bookshelf. If attention is paid to two boards in the bookshelf, a plurality of structures of the balanced interface circuit 20 may exist between the two boards, and if attention is paid to a certain part, the transmission-side board (PKD2) is formed. When the other substrate is focused on, another substrate may be the receiving substrate (PKR2).

In FIG. 1, the balanced interface circuit 20 includes a transmission side board PKD2, a back plane board BP2, and a reception side board PKR2.

A signal transmitting circuit (driver) DV2 is mounted on the transmitting substrate PKD2, and the receiving substrate PK
A signal receiving circuit (receiver) RV2 is mounted on R2.

The input terminal e of the signal receiving circuit RV2
A selector SEL2 is arranged on the side of 1, e1 '. The selector SEL2 automatically switches the connection destination of the terminal t3 between the terminals t1 and t2 and changes the connection destination of the terminal t5 to the terminals t6 and t4 in accordance with the level of the voltage supplied to the control input terminal S1. Has the ability to switch between.

That is, when the voltage supplied to the control input terminal S1 is at the L level,
When the terminal t3 is connected to t2 and the terminal t5 is connected to t4 to be in a connected state (of the signal line T2), when the voltage supplied to the control input terminal S1 is at the H level, the terminal t3 is connected to t1. The connection is made and the terminal t5 is connected to t6 to be in the protection state (of the signal receiving circuit RV2).

The selector SEL2 has terminals t1 to t3.
The configuration is such that two selectors, a selector 35 of a portion and a selector 36 of a portion of terminals t4 to t6, are combined.

Switching between two connection destinations in the selector SEL2 (switching between the two selectors 35 and 36)
From the viewpoint of maintaining the equilibrium, it is preferable to carry out the treatment simultaneously.

In order to improve the accuracy of the synchronization, it is desirable that the two selectors 35 and 36 be formed in the same IC (integrated circuit) package.

The terminal t1 is the other end of a damping resistor (pull-up resistor) RD1 having one end connected to the power supply voltage Vcc, and the terminal t2 is connected to a signal line T2 (rc2). The terminal t6 is the other end of a damping resistor (pull-down resistor) RD2 having one end grounded, and the terminal t4 is connected to a signal line T2 (rc2 ').

Assuming that the signal line rc2 is a signal line in the outward direction, the signal line rc2 'is a signal line in the backward direction. In the present embodiment, the two signal lines rc2 and rc2 ′
The target signal is transmitted in the normal mode transmission using. This is because the normal mode is superior to the common mode in that an electric signal can be transmitted without deformation.

The selector SEL2 on the receiving side substrate PKR2
A control line C2 connected to the control input terminal S1 of the transmission side substrate PK
Grounded on D2. The control line C2 is connected to the other end of a damping resistor (pull-up resistor) RD3 having one end connected to the power supply voltage Vcc on the receiving side substrate PKR2. The value of the damping resistor RD3 may be, for example, about 10 kΩ.

Similarly to the control line C2, the signal line T2 is also arranged on the receiving board PKR2, the backplane board BP2, and the transmitting board PKD2 via the connectors 21, 22, 23, 24.

That is, the signal line rc2 connected to the terminal t2 of the selector SEL2 on the receiving side substrate PKR2
Is connected to the output terminal b2 of the signal transmission circuit DV2 on the transmission-side substrate PKD2, and is connected to the selector SEL on the reception-side substrate PKR2.
The signal line rc2 ′ connected to the second terminal t4 is wired on the backplane substrate BP2, and the transmission side substrate PKD
2 is connected to the output terminal b2 'of the signal transmission circuit DV2.

The damping resistors RD1, RD2
May be about several tens Ω to several hundred Ω as an example.
From the viewpoint of balance, it is desirable that the values of RD1 and RD2 are the same.

The connectors 24 and 23 have an internal structure as shown in FIG.

In FIG. 3A, female contacts 27, 28, and 29 are provided on the female connector 24 side, and male contacts 30, 31, and 32 are provided on the male connector 23 side. The female contact 27 is formed shallower than the other two female contacts 28 and 29, and the male contact 30 is formed shorter than the other two male contacts 31 and 32.

This is because, when the transmitting side board PKD2 is removed, one of the three sets of male and female contacts 27 and 30 is separated first, and the transmitting side board PKD2 is separated.
When the KD2 is inserted, one of the three sets of male and female contacts 27 and 30 is finally connected (contacted).

FIG. 3A shows a state in which the female connector 24 of the transmitting side board PKD2 shown by a solid line is completely attached to the male connector 23 of the backplane board BP2 shown by a broken line. Is shown.

The internal structure of the connectors 22 and 21 is substantially the same as that shown in FIG.

That is, in the connectors 21 and 22, the backplane board BP2 is connected to the receiving board PKR2.
Is removed, the control line C2 is disconnected first, then the signal lines rc2 and rc2 'are disconnected almost simultaneously. Conversely, when the receiving-side substrate PKR2 is inserted into the backplane substrate BP2, the signal line rc2 is disconnected. And rc2 'are connected almost simultaneously, and then the control line C2 is connected.

The input terminal e1 of the signal receiving circuit RV2
A termination resistor RT2 is inserted between and e1 '. The value of the termination resistor RT2 may be, for example, about several tens Ω to several hundred Ω.

The purpose of the terminating resistor RT2 is to prevent the influence of reflection to eliminate the disturbance of the waveform on the signal line T2, to improve the noise resistance of the signal receiving circuit RV2, and to reduce the unnecessary radiation from the signal line T2. And so on.

Here, regarding the noise resistance, since the input impedance of the signal receiving circuit RV2 is generally several tens kΩ or more, the terminal t
3, the input impedance on the right side as viewed from t5 is reduced, and the voltage induced when noise of the same power is loaded is reduced. In this sense, the terminating resistor RT
The smaller the value of 2, the better.

However, the provision of the terminating resistor RT2 requires the signal transmission circuit DV2 to have a current driving capability sufficient to drive the terminating resistor RT2.
In consideration of the increase in current driving capability and power consumption and the increase in reflection, the value of the terminating resistor RT2 cannot be reduced too much.

Hereinafter, the operation of the present embodiment having the above configuration will be described.

(A-2) Operation of the Embodiment In the state shown in FIG. 1 in which the connectors 21 and 22 and the connectors 23 and 24 are completely mounted, the potential of the control input terminal S1 becomes L due to the voltage drop of the damping resistor RD3. Level, the selector SEL2 is connected to the terminal t3
And t2 while connecting the terminals t5 and t4.

At this time, the signal transmitted through the signal line T2 changes according to the signal supplied to the input terminal a2 of the signal transmission circuit DV2, and the signal reception circuit R2 changes according to the change.
The signal output from the output terminal d2 of V2 changes.

Since the interface circuit 20 is of a balanced type, ideally, for example, when the potential of the signal line rc2 is 3 V (volts) and the potential of the signal line rc2 'is 0 V, it indicates a high level (H). The H level is output from the output terminal d2 of the receiving circuit RV2, and when the potential of the signal line rc2 is 0 V and the potential of the signal line rc2 'is 3 V, it indicates a low level (L). The L level is output.

That is, the signal line T2 (rc2, rc2 ')
Is a normal mode signal transmitted in the form of a difference voltage (or difference current) between rc2 and rc2 ′.

By adopting the balanced configuration, it is possible to prevent the common mode noise from changing to the normal mode.

All noises on the signal line T2 etc.
Irrespective of the cause of the occurrence, it can be classified into common mode noise and normal mode noise from the viewpoint of the transmission mode. Whether the signal is noise or a signal to be transmitted, the signal in the normal mode includes both signal lines rc2 and rc.
c2 ′, and the common mode signal appears on both signal lines rc
2, it can be defined as appearing between rc2 'and ground.

Since common mode noise is noise induced equally in two signal lines, the common mode noise does not adversely affect an electronic circuit as long as the common mode noise is common mode noise. However, this common mode noise often changes to normal mode noise in the process of being transmitted through an electronic circuit or a signal line.

On the other hand, the normal mode noise is the same as the signal to be transmitted as far as the transmission mode is concerned, so that the electronic circuit tends to be affected by the signal.

Therefore, it is necessary to prevent the common mode noise from changing to the normal mode noise by maintaining the balance.

Next, a case where the transmitting side substrate PKD2 in the energized state is removed from the state shown in FIG. 1 will be described. At this time, the transmitting-side board PKD2 itself to be removed is also in the energized state, and the PBX exchange system such as the receiving-side board PKR2 is energized and operated.

The connectors 24 and 23 in the state of FIG. 1 are in the state of FIG.

In the direction of arrow DX in FIG.
When the KD2 is removed, the female contact 27 and the male contact 30 are separated from each other as shown in FIG. At this point, the female contact 28 and the male contact 31 and the female contact 29 and the male contact 32 are still in contact (coupling).

That is, in the state of FIG. 3B, the control line C2 is disconnected, but the two signal lines rc2 and rc
2 'is still connected.

This is, as described above, the female contact 27.
Is formed shallower than the other two female contacts 28, 29, and the male contact 30 is formed shorter than the other two male contacts 31, 32.

Thereafter, the transmitting side board PKD2 is
When the female contact 28 and the male contact 31 are further removed in the direction of the arrow DX than the state shown in FIG. 3B, the female contact 29 and the male contact 32 are also separated almost at the same time as the female contact 28 is separated.

However, as is well known, the female contact 28 and the male contact 3
It is difficult to obtain complete synchronism for the separation of 1 and the separation of the female contact 29 and the male contact 32. Therefore, instantaneously, a state occurs in which one of the contacts is in contact but the other is not in contact (or a state in which the contact resistance of the two male and female contacts slightly fluctuates). It is considered that this causes instantaneous imbalance and causes noise in normal mode.

In order that the unbalance does not adversely affect the signal receiving circuit RV2, it is necessary to disconnect the female contact 27 and the male contact 30 and disconnect the control line C2 sufficiently earlier than the occurrence of the unbalanced state. There is.

When the control line C2 is disconnected, the selector SE
An H level voltage substantially equal to the power supply voltage Vcc is supplied to the control input terminal S1 of L2. Thus, the selector SEL2 disconnects the terminal t3 from t2 and connects to t1, and disconnects the terminal t5 from t4 and connects to t6.

That is, a protection state is established in which the input terminal e1 is connected to the damping resistor RD1 and the input terminal e1 'is connected to the damping resistor RD2.

In this protection state, the input terminal of the signal receiving circuit RV2 is disconnected from the signal line T2, so that the signal line T2 carries normal mode noise, common mode noise, or noise. Even if the voltage level of the signal line T2 is uncertain due to other causes, the signal receiving circuit RV2 is not adversely affected.

Further, even if there is noise directly received at the input terminals e1 and e1 'and the selector SEL2 without passing through the signal line T2, the signal receiving circuit RV2 of the present embodiment is capable of responding to the noise. Signal receiving circuit RV
Noise resistance is higher than 1 and operation is stable.

The reason is that the damping resistors RD1, RD2
, The input terminals e1 and e1 ′ of the signal receiving circuit RV2 have lower ground resistance and the same power than the input terminals c1 and c1 ′ of the conventional signal receiving circuit RV1 when the transmitting-side board PKD1 is removed. This is because the voltage induced by noise is low.

Most of the noise directly received by the input terminals e1 and e1 'and the selector SEL2 is considered to be common mode high frequency noise. If it is not a high frequency, it is unlikely that it will directly enter the input terminals e1, e1 ', etc., where the signal line is disconnected. This is because there is a high possibility that they will act and become common mode noise.

Since Vcc can be regarded as ground at high frequencies, this common mode noise is attenuated via damping resistors RD1 and RD2 before being changed to normal mode noise, and is substantially removed. Can be expected.

Even in the case of non-high frequency noise or normal mode noise, the effects can be reduced and substantially eliminated by the damping resistors RD1 and RD2.

In this embodiment, the signal supplied to the input terminal e1 in this protection state is the H level.
Since the signal supplied to the input terminal e1 'is at the L level,
The signal output from the output terminal d2 of the signal receiving circuit RV2 is fixed at the H level.

Next, the transmitting-side board PK completely removed will be described.
A case where D2 is inserted (mounted) will be described.

In case of mounting, contrary to removal, FIG. 3 (B)
From the state shown in FIG. 4A to the state shown in FIG. In FIG. 3B, the direction in which the transmission side board PKD2 and the connector 24 move is the direction of the arrow DY.

At a point shortly before the state of FIG.
There is a possibility that the above-mentioned momentary unbalanced state may occur. In this case, the selector S of the interface circuit 10
EL2 is in the protection state.

At a point slightly after FIG. 3B,
Since the male and female contacts 27 and 30 come into contact with each other, the control line C
2 is connected, and the selector SEL2 shifts to the connection state.

Although the active insertion and removal of the transmission-side board PKD2 (removal of the connectors 23 and 24) has been described above, the same applies to the active insertion and removal of the reception-side board PKR2.

However, in the case of insertion / removal of the receiving side board PKR2,
The connector 21 is inserted and removed from the connector 21 opposite to the side where the control line C2 is grounded. Therefore, in FIGS. 3A and 3B, the side of the connector 24 (22) is stationary, and the side of the connector 23 (21) moves.

(A-5) Effects of the Embodiment As described above, according to the present embodiment, it is determined whether the state of the signal line T2 is the H level or the L level due to the influence of noise or the like at the time of hot insertion and removal. Even without this, the output of the signal receiving circuit is stably fixed at the H level, so that no problem occurs on the receiving side substrate and the reliability of the interface circuit can be improved.

Further, since the interface circuit of this embodiment has a very simple configuration, the circuit scale is small.
Excellent cost and feasibility.

In other words, the present embodiment reduces the influence of noise and the like mixed therein by preventing the ground resistance of the input terminals (e1, e1 ') of the signal receiving circuit from becoming too high during hot insertion and removal. Thus, the operation of the signal receiving circuit can be stabilized.

(B) Other Embodiments In the above embodiment, the signal transmission circuit DV2 is a simple driver. However, the present invention can be applied to a case where the signal transmission circuit DV2 is a three-state gate. .

This is a case where a common signal line T2 is connected to the output terminals of a plurality of three-state gates and the signal line T2 is shared.

In the above embodiment, the interface circuit 20 is of a balanced type. However, depending on conditions such as the surrounding noise environment, the balance may not be so strict.

As for the balance, the above embodiment is a balanced interface in the sense that signals are transmitted by a pair of signal lines. However, the present invention provides an unbalanced interface for transmitting signals by a single signal line. It can also be applied to type interfaces.

Further, in the PBX exchange according to the above embodiment, the number of the boards constituting the system is about 20. However, the PBX exchange can be applied to a smaller system in which the number of the boards to be inserted and withdrawn is about one to several. The present invention can be applied. Also, it is needless to say that the present invention may be applied to a system different from the PBX exchange. Further, the system of the present invention need not be a bookshelf type configuration.

In the above embodiment, the output of the signal receiving circuit RV2 is fixed at the H level in the protection state. However, it is obvious that the output may be fixed at the L level.

Further, with respect to the configuration of the control line C2, in the above embodiment, the grounding is performed on the transmitting side substrate PKD2,
Pulled up on the receiving side board PKR2.
A configuration is also possible in which the connection is made to Vcc on KD2 and pulled down on PKR2. However, in this case, the control input terminal S1 is at the H level in the inserted state and is at the L level in the removed state.
Level.

The connectors 21 to 24 of the above embodiment are
Regarding the configuration of the part, it is natural that the male and female contacts may be exchanged.

In the above embodiment, the backplane board exists between the transmitting board and the receiving board.
This backplane substrate is not necessarily an essential component of the present invention.

Further, in the above embodiment, the means for responding to the transient phenomenon in which the state (H, L) of the signal line is uncertain due to the active insertion / removal and the noise or the like generated at the time of the active insertion / removal is provided. Can provide a means for coping with the case where such a transient phenomenon occurs other than the hot insertion and removal.

For example, it is considered that such a transient phenomenon can occur in an operation process such as a power-on reset.

That is, the present invention relates to a board that is inserted into and becomes part of a system, is removed and separated from the system, and a balanced first board that connects the board to the system.
The present invention can be widely applied to a transmission interface device that includes a second signal line and mediates signal transmission between the system and the board.

[0092]

As described above, according to the present invention, the reliability of the transmission interface device can be improved with a small-scale configuration, and the cost and the feasibility are excellent.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an interface circuit according to an embodiment.

FIG. 2 is a schematic diagram showing a configuration of a conventional interface circuit.

FIG. 3 is a principle explanatory view showing a mechanical and electrical configuration of a connector portion in the embodiment.

[Explanation of symbols]

10, 20 interface circuit, 21-24 connector, 27-29, 30-31 contact, 35, 36
... selector, C2 ... control line, T2 (rc2, rc2 ')
... signal line, PKD2 ... transmission side board, PKR2 ... reception side board, BP2 ... backplane, DV2 ... signal transmission circuit,
RV2: signal receiving circuit, RT: terminating resistor, RD1 to RD
3: Damping resistance, e1, e1 ': input terminal, SEL
2 ... Selector.

Claims (1)

[Claims] 1. A system comprising: a board that is inserted into and becomes part of a system; is withdrawn and separated from the system; and first and second balanced signal lines connecting the board and the system. In a transmission interface device for mediating signal transmission between boards, insertion / extraction detection means for detecting insertion / removal of the board; and at least two connection means arranged on the board and connected to the first and second signal lines. A signal receiving unit having an input terminal, and when the insertion / removal detection unit detects removal of the board, the input terminals are simultaneously disconnected from the first and second signal lines and a predetermined potential is applied. In both cases, when the insertion / extraction detection unit detects insertion of the board, application of the predetermined potential to the input terminals is stopped, and the input terminals are simultaneously connected to the first and second signal lines. A transmission interface device comprising: connection selection means.