JP2005198134A - Interface device and interface control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a capacitor to be made adaaptable to both of connection and elimination automatically in accordance with conditions of an opposite device in an interface device for a LAN with which an information processor performs a communication with other devices via pair wire terminating by transformer coupling and an interface control method. <P>SOLUTION: In the interface device, one terminal of the capacitor is connected to a mid-point tap on a present device side of the transformer coupling, a switch is provided between another terminal of the capacitor and a ground terminal, and a means for setting information for controlling on/off of the switch is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an interface apparatus and an interface control method using a transformer coupled pair line as a LAN transmission path connected to an information processing apparatus.

  When transmitting and receiving data by connecting multiple information processing devices (computers) via a LAN (Local Area Network), balanced transmission using two pair wires (line pairs) as the transmission path for electrical signal transmission Is used, and the technique of terminating by transformer coupling is used.

  As a technique for reducing the effect of unbalanced noise in a transmission line that terminates in a transformer using such a paired wire (balanced paired wire), a technology for grounding the center tap of one winding of the transformer coupling is known. (See Patent Document 1). In a balanced transmission circuit, a technique for removing noise by connecting a capacitor to the center tap of a transformer and grounding is known (see Patent Document 2), and will be described with reference to FIG.

  FIG. 4 shows a configuration example of a LAN interface using a pair line. In the figure, 80 is a pulse transformer on the device A side (transmission side), 80a is a primary winding, 80b is a secondary winding, 81 and 82 are pair wires, and 83 is a device B side (reception side). , 83a is a primary winding, and 83b is a secondary winding. Reference numeral 84 denotes a midpoint tap of the primary side winding of the transmission-side pulse transformer 80 and a capacitor C1, 85 provided between the ground and a midpoint tap of the secondary side winding of the receiving-side pulse transformer 83. Although the capacitor C2 is provided between the grounds, 84 and 85 may not be provided. Note that FIG. 4 shows only the configuration for transmission in one transmission direction, but in reality a similar configuration is provided for transmission in the reverse direction, and transmission signals to each pulse transformer not shown are shown. And an interface (which has control functions such as a physical layer and a MAC (Media Access Control) layer) that transmits and receives a reception signal from the pulse transformer, is connected to the IO controller of the computer.

When a signal is transmitted through the pair wires 81 and 82 using a pulse transformer as shown in FIG. 4, common noise may be applied. As a countermeasure for the counterpart device having many errors due to common noise, a capacitor 84 is provided between the center tap of the primary winding of the pulse transformer 80 on the device A side and the ground, and the pulse transformer on the device B side is provided. A capacitor 85 is provided between the midpoint tap of the secondary winding of 83 and the ground so that common noise is removed through each capacitor.
JP 58-1441038 A Japanese Patent No. 2670166 (FIGS. 3 to 5)

  On the other hand, the standard specification of LAN does not stipulate that a capacitor must be connected to the center of the pulse transformer and connected to the ground.

  However, when distant devices are connected with a pair of wires as shown in FIG. 4 and terminated with a pulse transformer, there is noise between the grounds of the devices, and there is a shield or FG line (frame ground: device ground terminal). If a cable with no cable is used, a device with a capacitor becomes a noise source. The influence of noise due to the presence or absence of a capacitor will be described with reference to the diagram for explaining the influence of the capacitor shown in FIG.

  In FIG. 5, the device A side and the device B side are connected by paired wires 81 and 82, the pulse transformer is not shown, RA represents an equivalent resistance existing in the route on the device A side of common noise, and RB is It represents an equivalent resistance existing in the route on the device B side of common noise, 84 is a capacitor C1 provided on the device A side, and 85 is a capacitor C2 on the device B side, but as shown by a dotted line, the device B May or may not be provided on the side. 86 is a noise source on the pair wire 82. Note that FG (frame ground) and SG (signal ground) are short-circuited in each device.

  When there is a noise source 86 between the device A side and the device B side, the capacitor C1 is on the device A side, and the capacitor C2 is not on the device B side, there is no noise escape on the device B side, and the arrow (→) As shown in Fig. 8, there is a possibility that the noise becomes large and errors occur frequently on the device B side. In this case, the provision of the capacitor C1 in the device A results in providing a noise source that increases the extra common mode noise to the device B. In order to cope with this, when the capacitor C1 on the device A side is removed, if it is connected to a device equipped with a capacitor on the other side (device B side), this time, it becomes the position of the device B described above. It will be affected by noise.

  That is, a pattern that does not cause a problem due to noise in the mode shown in FIG. 5 is one of the following two cases.

  (1) Do not install capacitors on both devices.

  (2) Install capacitors on both devices.

  The case (1) where no capacitor is provided for both devices is not the best as a countermeasure for common mode. However, as a result of the large noise in both sides, the noise decreases, and the problem of noise due to the pattern (1) shown in FIG. Difficult to manifest. In addition, in the case where capacitors are provided in both of the above (2), the two devices are short-circuited in an alternating current by the capacitors in the pattern shown in (2) of Fig. 5, and noise does not spread outside the capacitors. ， No trouble caused by common noise.

  On the other hand, in order to eliminate the influence of common noise when connecting to an unspecified device whose specifications are not fixed or whether a capacitor is attached to the middle point of the pulse transformer, check the other party's condition and attach a capacitor. There was a problem of having to work to remove it.

  At present, devices with and without capacitors are already on the market. As a countermeasure, either the fixed mounting or non-mounting of the capacitors narrows the corresponding market, and optional devices. It does not match the actual situation of personal computer business based on selection and configuration.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a LAN interface device and an interface control method capable of automatically connecting / removing a capacitor according to the conditions of a counterpart device.

  FIG. 1 shows the principle configuration of the present invention. In the figure, reference numeral 1 denotes a termination unit in which the pair lines 3a and 3b forming the LAN transmission line are terminated by transformer coupling, 2 is an interface between the transformer coupling termination unit 1 and an input / output control unit 5 described later, and 20 is a transformer. A capacitor having one terminal connected to a midpoint tap on the coupling device side, and 21 is electrically on (connected) or off (disconnected) between the other terminal of the capacitor 20 and a ground (ground) terminal Switches to be switched, 3a and 3b are paired wires, 4 is an information processing unit that transmits and receives data to and from other devices via the LAN, and 40 is a capacitor that connects or disconnects a LAN transformer coupling termination unit. A capacitor adjusting unit for adjusting the above, 40a is a test means for each switch state, 40b is a test result determining means, and 40c is a switch that has been determined to be of good quality by the test result determining means 40b. Switch control means for performing control to set the switch setting unit 51 in the state, 5 is an input / output control unit for controlling transmission and reception of data via the LAN, 50 is a communication unit for communicating with other devices via the LAN, 51 is a switch setting unit for generating an output for controlling the switch 21 according to the setting state, and 6 is a transformer coupling termination unit of the counterpart device connected by the pair wires 3a and 3b. .

  In the present invention, when a LAN transmission line is configured with a pair of wires and terminated with a transformer coupling, a capacitor is connected to the midpoint of the primary side of the transformer, and a switch for turning on and off between the capacitor and the ground is provided. By checking the state of communication when the switch is turned on and off, identifying the state where good communication characteristics can be obtained, and switching the switch to that state, it is possible to match the state of the counterpart of the paired wire , Good data transmission becomes possible.

  When the capacitor adjustment unit 40 of the information processing unit 4 is driven, a test is performed by the switch state test means 40a. In this case, by first setting the switch setting unit 51 of the input / output control unit 5 to the on state, the switch 21 is turned on and the capacitor 20 is connected to the middle point of the transformer of the termination unit 1 of the transformer coupling. In this state, the test means 40a according to the switch state performs test communication with the counterpart device via the termination unit 1 and the paired wires 3a and 3b, and obtains and stores a result representing the quality of communication. Next, the switch state-specific test means 40a sets the setting information of the switch setting unit 51 to the OFF state for the input / output control unit 5 to turn off the switch 21, and the capacitor is not connected to the midpoint of the transformer. The same test communication as that performed when the switch 21 is turned on via the paired wires 3a and 3b is performed, and a result representing the communication quality is obtained and stored. Next, the test result discriminating means 40b discriminates the test result by the switch state-specific test means 40a. When a switch state with a good result is detected, the switch control means 40c is notified of the state, and the switch control means 40c is turned on. The switch setting unit 51 of the output control unit 5 is set to the notified state. As a result, the switch 21 is switched on or off.

  According to the present invention, when connecting to a counterpart device by a paired line using a pulse transformer such as a LAN, depending on each state whether or not the capacitor is connected to the midpoint of the pulse transformer of the own device and the capacitor is grounded. By performing a communication test, it is possible to determine whether or not a capacitor to the middle point of the pulse transformer on the other device side is connected. By switching the state on the own device corresponding to the other device side, Communication reliability can be improved with good communication quality.

  FIG. 2 shows the configuration of the embodiment. 1 is a transformer coupling termination unit, 1a is a reception transformer, 1b is a transmission transformer, 2a is a physical layer control unit, and 20a and 20b are capacitors each having one terminal connected to a midpoint tap of the transformers 1a and 1b. , 21a, 21b constitute the switch 21 of FIG. 1, FETs (Field Effect Transistors) for switching whether or not the other ends of the capacitors 20a, 20b are connected to the ground, 2b, a MAC layer control unit, 3a , 3b are receiving pair wires, and 3c, 3d are transmitting pair wires. 4a is a CPU, 4b is a memory control unit, 4c is a memory for storing programs and data, 5 is an input / output control unit (IO control unit), 50 is a communication unit, 51a is a GPIO provided in the input / output control unit 5 This is a register for setting information of an input / output pin called “General Purpose Input Output”, and information for controlling the FETs 21a and 21b constituting the switch is set by one bit therein.

  The memory control unit 4b and the input / output control unit 5 are peripheral circuits of the CPU 4a and are integrated circuits called chip sets. The memory control unit 4b has a memory control function, and the input / output control unit 5 is a hard disk or a propppy disk. The GPIO is an input / output pin for inputting / outputting a system-specific signal, and can be switched between input and output depending on whether input or output is fixed or designated. In this embodiment, one bit of the register 51a is used for switching the capacitor as one signal of the GPIO signal line.

  The other ends of the capacitors 20a and 20b having one terminal connected to the center tap of the transformer coupling are connected to the FET 21a provided as a switch, and the other end of the FET 21b connected in series to the FET 21a is connected to the ground terminal. By switching a 1-bit GPIO signal from the register 51a of the input / output control unit 5, a state in which a capacitor is added or a state in which the capacitor is deleted is set.

  FIG. 3 is a processing flow of the capacitor switching control, which is executed by the program stored in the memory 4c in the CPU 4a of FIG.

  First, the registers Ra and Rb are set to 0, and the capacitor is removed (the control bit of the register 51a of the input / output control unit 5 is set to “0” to turn off the switches 21a and 21b). (S1 in FIG. 3). Next, a command for confirming transmission quality is executed (S2 in FIG. 3). In this embodiment, as a command for confirming transmission quality, an echo request message is sent to the partner and a message for receiving an echo response message from the partner is sent from the input / output control unit 5 to the MAC layer control unit 2b, physical layer. The response time (response time) from the time when the transmission is transmitted through the control unit 2a to the time when the response from the other party is returned is measured and held in the register Ra. (S3 in FIG. 3). Next, the capacitor is added ("1" is set to the control bit of the register 51a of the input / output control unit 5 so as to turn on the switches 21a and 21b) (S4 in FIG. 3). A similar command is executed (S5), the response time from the other party is measured, and the result is held in the register Rb (S6).

  Subsequently, it is determined whether or not Ra ≦ Rb (S7 in FIG. 3), and if it is established (response time Ra when the capacitors 20a and 20b are removed is shorter), control for removing the capacitor is performed ( In the case of S8), if it is not established (a state in which a capacitor is added), the processing ends as it is (a state in which a capacitor is added in S4).

  The echo request message described as an example of the test communication executed in the above steps S2 and S5 is an ICMP (Internet Control Message Protocol) protocol that checks whether the transmitted data has correctly reached the partner computer. Use echo request messages. The counterpart device that has received this request is to send back an echo reply message. A command (tool) using such a message is called PING (Packet InterNetwork Groper).

  (Supplementary note 1) In a LAN interface device in which an information processing unit communicates with other devices via a pair of wires terminated with transformer coupling, one terminal of a capacitor is connected to a midpoint tap on the transformer coupling own device side. A LAN interface apparatus comprising a means for connecting and providing a switch between the other terminal of the capacitor and a ground terminal, and setting information for controlling on / off of the switch.

  (Supplementary Note 2) A LAN interface characterized in that the means for setting information for controlling on / off of the switch is constituted by a register for setting information for input / output control set by the information processing section. apparatus.

  (Supplementary Note 3) In the LAN interface control method for the information processing unit to communicate with other devices via a pair of wires terminated by transformer coupling, a ground is connected to the other end of the capacitor connected to the midpoint tap of the transformer coupling. A switch for controlling connection with a terminal, and the information processing unit performs a test communication with the other device via the pair line in each of the on and off states of the switch to express the communication quality in each state A LAN interface control method, wherein the switch is controlled in a state where a good result is obtained by evaluating a result representing the quality of the test communication.

  (Additional remark 4) In Claim 2, as test communication with the other apparatus via the pair line, measuring a time from when a call is made to the other apparatus until a response is returned from the other apparatus A LAN interface control method.

It is a figure which shows the principle structure of this invention. It is a figure which shows the structure of an Example. It is a figure which shows the processing flow of capacitor | condenser switching control. It is a figure which shows the structural example of the interface of LAN using a pair line. It is a figure explaining the influence by a capacitor | condenser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transformer termination | terminus part 2 Interface 20 Capacitor 21 Switch 3a, 3b Pair line 4 Information processing part 40 Capacitor adjustment part 40a Switch state test means 40b Test result discrimination means 40c Switch control means 5 Input / output control part 50 Communication part 51 Switch Setting part 6 Termination part of transformer coupling of counterpart device

Claims (3)

In a LAN interface device for communicating with other devices via a pair line terminated by a transformer coupling in an information processing device,
One terminal of a capacitor is connected to a midpoint tap on the transformer-coupled device side, and a switch is provided between the other terminal of the capacitor and a ground terminal,
A LAN interface device comprising means for setting information for controlling on / off of the switch. In a LAN interface control method for communicating with other devices via a pair line terminated by a transformer coupling of an information processing device,
A switch for controlling the connection to the ground terminal is provided at the other end of the capacitor connected to the center tap of the transformer coupling,
The information processing device obtains a result representing the communication quality in each state by performing test communication with the other device via the pair line in each of the on and off states of the switch,
A LAN interface control method comprising: evaluating a result representing the quality of the test communication; and controlling the switch so that a good result is obtained. In claim 2,
A LAN interface control method, comprising: measuring a time from when a call is made to another device as a test communication with the other device via the pair line until a response is returned from the other device. .

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