JPH02301251A - Interface discrimination circuit - Google Patents

Abstract

PURPOSE:To easily discriminate the kind of the interface by discriminating whether the interface is a data terminator interface or a data terminal equipment interface depending on the difference of the output of a voltage comparator corresponding to the difference from the voltage level of a signal line. CONSTITUTION:A connector 5 is provided at one terminal of a DCE side cable 4 of a data terminator of a discrimination changeover circuit 3 including a voltage comparator and the connector 5 is coupled freely with a connector A of the DCE 1. Moreover, a connector 8 of a cable 7 at the side of a data terminal equipment DTE of the discrimination changeover circuit 3 is coupled removably with the connector 9 of the DTE 2. The DCE 1 and the DTE 2 include an interface respectively and the discrimination changeover circuit 3 discriminates the content of the interface for the DCE 1 and the DTE 2 to connect the both so as to be in matching with the content. Since the DTE interface or the DCE interface is discriminated by the voltage comparator, then the kind of the interface is recognized automatically.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to communication circuits in which the interface is a data termination equipment (DCE) interface or a data terminal equipment [(DT
E) This relates to an interface discriminating circuit for automatically discriminating whether it is an interface.

[Prior Art] A DTE is connected to a transmission line of a data communication circuit via a DCE. Connection between the DCE and DTE is typically accomplished by coupling one end of the cable to the DCE connector and the other end of the cable to the DTE connector.

DTE and DCE are, for example, JIS standards C6361 and E.
Interface specified by TA standard R8-232C (
(hereinafter referred to as the R1-232C interface).

[Problems to be Solved by the Invention] By the way, since the DCF and DTE are not fixedly connected, DTEs with the same configuration are not always connected to the DCE, and DTEs with different configurations may be connected. For example, when connecting a computer to a computer peripheral device, the same type of peripheral device may not always be connected to the computer, or the computer peripheral device may not always be connected to the computer.
It does not necessarily include an R3-232C interface designed as a TE interface, but may include an R3-232C interface designed as a DCE interface. If the R3-2320 interface of the computer peripheral device is a DTE interface or a DCE interface, the connection to the computer must be changed. In order to change the connection, the interface must first be determined. Now, Although the R3-232C interface has been described, similar problems exist with other interfaces.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a circuit that can easily determine whether an interface connected to a communication line is a DTE interface or a DCB interface.

[Means for Solving the Problems] To achieve the above object, the present invention determines whether an interface is a data termination equipment (DCE) interface or a data terminal equipment fi (DTE) interface, The device includes a voltage comparator connected to a signal line, and is configured to determine whether the interface is the data termination device interface or the data terminal device interface based on a difference in output of the voltage comparator corresponding to a difference in voltage level of the signal line. The present invention relates to an interface discrimination circuit characterized in that:

Further, in order to discriminate between a pair of interfaces, it is desirable to selectively connect the pair of interfaces to a common voltage comparator using a switch.

[Function] In the present invention, since the voltage comparator determines whether the interface is a DTE interface or a DCE interface, the type of interface can be automatically known.

[Embodiment] Next, a circuit for determining and switching between a DCE interface and a DTE interface according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.

FIG. 1 shows the connection relationship between DCEl and DTE2, both of which are connected to each other via an interface discrimination switching circuit 3 according to the present invention. That is, discrimination switching diagram F! A connector 5 is provided at one end of the DCE side cable 4 of @3, and this connector 5 is detachably connected to a connector 6 of the DCEl. In addition, the DT of the discrimination switching circuit 3
The connector 8 of the EflJ cable 7 is detachably connected to the connector 9 of the DTE 2.

DCEl and DTE2 each include an R3-232C interface.0 discrimination switching circuit 3 includes DCEl and DTE2, respectively.
The system is configured to determine the content (type) of the R3-232C interface of No. 2 and to connect the two in accordance with the content (type) of the R3-232C interface.

FIG. 2 shows in detail the configuration of the discrimination switching circuit 3 shown in FIG. 1, which consists of a discrimination circuit 10 and a cable switching circuit 11. One R8-232C interface 12 is included, for example, in a DCH of a personal computer, and the other R3-232C interface 13 is included in a DTE, such as a peripheral device of a personal computer. R3-
DCEIFJ connected to 2320 interface 12
The DTE side connector 9 connected to the connector 6 and the R3-232C interface 13 has terminals as shown in FIGS. 4 and 5. That is, each connector 6.9 has a safety ground terminal FG, a transmission data terminal SD, a reception data terminal RD, a transmission request terminal R3, a transmission permission notification terminal C8, a signal ground terminal SG, a reception line signal detection terminal CD, and a data terminal ready. Each has a terminal ER. Note that in FIGS. 4 and 5, arrows attached to terminals indicate signal directions, and 1 to 8.20 indicate bin numbers.

In FIG. 2, the discrimination circuit 10 is connected to a DCE side SD signal line 14 and a DCE side RD signal line 15, as well as a DTEIFISD signal line 16 and a DTE side RD signal line 1.
7 is connected. DTE side SD signal line 16 and R
, D signal lines 17 are connected to the R3-232C interface 13 via the switching circuit 11 and signal lines 18 and 19. In addition, signal lines 20.21 other than SD and RD of the DCEffll R3-232C interface 12 and the DTE side R3-2320 interface 13 are connected to the switching port 1i411.
connected via.

The determination circuit 10 determines DCEf! based on SD and RD. I
! Determining whether the lR3-232C interface 12 is functioning as the DTE side interface, and
DTE side R3-232C interface 13 is DCEI
II! It is configured to determine whether or not it has an I interface function, and to provide the result of this determination to the switching circuit 11 via a control line 22. The switching circuit 11 is configured to switch the connection between the R3-232C interfaces 12 and 13, as shown in FIG. 4 or 5, for example.

As shown in FIG. 3, the discrimination circuit 10 includes first to sixth switches 23.24.25.26.27.28,
a fourth voltage comparator 29.30.31.32, a first and second OR gate 33.34 and a first and second resistor 3
5.36, a microcomputer 37, and first and second reference voltage sources 38.39. The first and second switches 23,24 are connected to each other and
The third and fourth switches 25.26 are connected in series to the signal line 14.16, and the third and fourth switches 25.26 are connected to each other and the RD
It is connected in series to signal line 15.17.

The non-inverting input terminal of the first comparator 29 is connected to the first reference voltage source 38, and the inverting input terminal is connected between the first and second switches 23, 24. The non-inverting input terminal of the second comparator 30 is connected to the first and second switches 23
．． 24, and the inverting input terminal is connected to a second reference voltage source 39. The non-inverting input terminal of the third comparator 31 is connected to the first reference voltage source 38, and the inverting input terminal is connected between the third and fourth switches 25, 26. The non-inverting input terminal of the fourth comparator 32 is connected between the third and fourth switches 25 , 26 , and the inverting input terminal is connected to the second reference voltage source 39 .

The output terminals of the first and second comparators 29.30 are connected to the first O
The output terminals of the third and fourth comparators 31 and 32 are connected to the microcomputer 37 via the R gate 33, and the output terminals of the third and fourth comparators 31 and 32 are connected to the microcomputer 37 via the second OR gate 34.
It is connected to the.

The first resistor 35 is connected to the inverting input terminal of the first comparator 29 and the non-inverting input terminal of the second comparator 30 via the fifth switch 27, and the second resistor 36 is connected to the sixth are connected to the inverting input terminal of the third comparator 31 and the non-inverting input terminal of the fourth comparator 32 via the switch 28 .

The microcomputer 37 includes ROM and RAM,
The first to sixth switches 23 to 23 according to a predetermined program
24 on/off control, DTE interface and DC
A signal indicating discrimination with the E interface is applied to the switching circuit 11 in FIG. 2 via the control line 22.

The first reference voltage source 38 is a circuit that provides a negative threshold voltage of the R3-232C interface 12.13, and the second reference voltage source 39 is a circuit that provides a negative threshold voltage of the R3-232C interface 12.13. This is a circuit that provides a threshold voltage. The negative threshold voltage of the R3-2320 interface 12.13 is -3V, and the positive threshold voltage is +3V. Therefore, voltages of −3V or higher and +3V or higher are effective. Note that the SD line 14.16 and the RD line 15.17 in FIG. 3 correspond to those indicated by the same reference numerals in FIG. connected to. Here, the receiving circuit is an R□ receiving circuit of a DTEtR device or an SD line receiving circuit of a DCE device, and the transmitting circuit is an SD line transmitting circuit of a DTE device or an RD line transmitting circuit of a DECtll device.

The values of the first and second resistors 35.36 are the SD signal 111
4 and the RD signal line 15, a transmitting circuit is connected to the first and third
, when the fifth and sixth switches 23, 25, 27, 28 are in the on state, the voltage at point A of the SD signal line 14 and point B of the RD signal line 15 is the positive voltage of the first reference voltage source 3. The voltage of the lower and second reference voltage sources 39 or higher, that is, the SD flaw signal and RD
It is set so that the threshold voltage on the minus side of the signal is -3V or less, and the threshold voltage on the plus side of the signal is greater than +3V. Also, the values of the first and second resistors 35.36 are S
When a reception circuit or a pull-up reception circuit is connected to the D signal line 14 and the RD signal line 15, and the first, third, fifth, and sixth switches 23, 25, 27, and 28 are in the on state. , point A of the SD signal line 14 and point B of the RD signal line 15
The voltage at the point is between the voltage of the first reference voltage source 38, that is, the negative threshold voltage (-3V), and the voltage of the second reference voltage source 39, that is, the positive threshold voltage (+3V). is set to .

FIG. 6 shows a part of the switching circuit 11, which includes switches S1, S2, S3, and S4 for changing the connection between the SD signal line 16.18 and the RD signal line 17.19. Switch S1 is connected between SD signal lines 16.18, switch S2 is connected between RD signal lines 17.19, and switch S3 is connected between RD signal line 17 and SD signal line 18.
The switch S4 is connected between the SD signal line 16 and R
It is connected between the D signal line 19 and the D signal line 19 . switch S1,
S2 is responsive to a switching signal applied from control line 22;
Switches S3 and S4 are responsive to the output of a NOT circuit 40 connected to control line 22. Therefore, switch $1, S2
and switches S3 and S4 operate inversely to each other. In addition,
SD signal line 16.18 and RD signal line 17.19 in Figure 6
correspond to those indicated by the same reference numerals in FIG.

Next, the operation will be explained.

In accordance with a predetermined program, the microcomputer 37 connects R3-232 to both ends of the discrimination switching circuit 3 in FIG.
Determine whether the R3-232C interface 12.13 is connected, and then connect the R3-232C interface 12.13.
13 is a DCE interface or a DTE interface.

First, when determining whether or not the R3-232C interface 12 is connected, the microcomputer 37
by the first, third, fifth and sixth switch 23.2
5.27.28 is turned on, the second and fourth switches 24.26 are turned off, R3- of DCF, 1
If the 232C interface 12 is connected, the SD
A transmitting circuit (
Since the output circuit) is connected, the standard voltage of R3-232C interface 12 (-3V or less, +3V or more)
is input to the SD signal line 14 or the RD signal line 15. S
When the standard voltage is input to the D flaw signal 14 or the RD signal line 15, the output of any one of the first to fourth comparators 29 to 32 becomes high level (H), and the output of one of the OR gates 33 and 34 becomes high level (H). The output also becomes high level (H), which is R3-232C.
The signal is input to the microcomputer 37 as a signal indicating that the interface 12 is connected.

When determining whether or not the R3-232C interface 13 is connected, the microcomputer 37 selects the second, fourth, fifth, and sixth switches 24, 26, .
When the R3-232C interface 13 is connected, the R3-232C interface 13 is connected to the SD signal line 16 or the RD signal line 17. 232C interface 13
The standard voltage (-3V or less, +3V or more) is obtained, and the first
~The output of one of the fourth comparators 29 to 32 becomes high level, and the output of one of the OR gates 33 and 34 also becomes high level, which indicates that the R3-2320 interface 13 is connected. The signal is sent to the microcomputer 37 as a signal indicating the signal.

When determining whether the R3-232C interface 12 has a DCE interface function or a DTE interface function, the first and fifth switches 23 and 27 are turned on, and the second and third switches 23 and 27 are turned on. , 4th,
The sixth switch 24.25.26.28 is turned off, at which time the R3-232C interface 12 is
In the case of an interface, since a transmitting circuit (output circuit) is connected to the SD signal line 14 of the R8-232C interface 12, R is connected to the first and second comparators 29 and 30.
The standard voltage of 8-232C interface 12 is input,
This is the reference voltage (-3
V) or the reference voltage set to the positive threshold (+3
V), the output of the comparator 29 or 30 becomes high level, the output of the OR gate 33 also becomes high level, and this is given to the microcomputer 37 as a signal indicating the DTE interface.

On the other hand, when the R3-232C interface 12 is a DCE interface, a receiving circuit or a pull-up receiving circuit is connected to the SD signal line 14 of the R8-2320 interface 12.

When the receiving circuit is connected, the SD signal line 14 has a value between the negative threshold voltage (-3V) and the positive threshold voltage (+3V), so the first and second The outputs of comparators 29 and 30 become low level (L), and O
The output of the R gate 33 also becomes low level, and this is sent to the microcomputer 3 as a signal indicating the DCB interface.
7 is given.

When determining whether the R3-232C interface 13 is a DCE interface or a DTE interface, the second
and the fifth switch 24.27 is turned on, and the first switch 24.27 is turned on.
, third, fourth and sixth switches 23.25.26.2
8 to the off state.

At this time, the R, S-232C interface 13 is
In this case, since the transmission circuit (output circuit) is connected to the SD signal line 16, the standard voltage (-
3V or less, +3V or more), one of the outputs of the first and second comparators 29.30 becomes high level, and the OR
The output of the gate 33 also becomes high level, and this is sent to the microcomputer 37 as a signal indicating the DTE interface.
Enter.

On the other hand, when the R3-232C interface 13 is a DCE interface, since the receiving circuit is connected,
The SD signal line 16 is in a state between the negative threshold voltage (-3V) and the positive threshold voltage (+3V),
The outputs of the first and second comparators 29 and 30 are at a low level, and the output of the OR gate 33 is also at a low level, which causes D
It is given to the microcomputer 37 as a signal indicating the CE interface.

The microcomputer 37 determines whether the R3-232C interface 12.13 is DTE or DCE, and provides a control signal to the switching circuit 11 based on this determination. Now, if a high-level signal is input to the control line 22 in FIG.
Signal lines 17 and 19 are also connected. On the other hand, if a low level signal is not input to the control line 22, the switches S1,
S2 is turned off, switches S3 and S4 are turned on, and the SD signal line 16 and RD signal line 19 are connected, and the RD signal line 17 and SD signal line 18 are connected. In addition, at the time of data communication after the determination is completed, the switches 23 and 24 are
．． 25 and 26 are turned on. For signal lines other than the SD signal line and RD signal line, follow the steps shown in Figure 4 or 5 as necessary.
Connection switching is performed as shown in the figure.

As described above, according to this embodiment, it is possible to automatically determine whether the interface is a DTE interface or a DCE interface, and furthermore, it is possible to automatically switch the connection between the two interfaces.

[Modifications] The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.

(1) As shown in FIG. 7, a plurality of DTE or DCE peripheral devices 42, 43, 44, 45 are connected to one personal computer 40 via an R3-232C switch 41, and the R3-232C switch 41 is the discrimination circuit 3 of the embodiment.
In this case, the R8-232C interface of the personal computer 40 and the interfaces of the peripheral devices 42 to 45 may be automatically connected without replacing cables, regardless of the type of interface. can be changed.

(2) Protocol analyzer 50 as shown in Figure 8
The present invention can be applied to the interface part of the protocol analyzer when connecting the line equipment W and 51. When performing a simulation with a protocol analyzer, program the DCE side, /DT
The E side is specified, but when this invention is used, the D side is automatically specified.
CE/DTE can be distinguished.

(3) Applicable to interfaces other than R3-232C.

[Effects of the Invention] As described above, according to the present invention, it is possible to automatically determine whether the interface is a DCE interface or a DTE interface.

[Brief explanation of drawings]

FIG. 1 shows a discrimination switching circuit and a DC circuit according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the relationship between the two R3-232C interfaces and the discrimination switching circuit, FIG. 3 is a circuit diagram showing the discrimination circuit in FIG. 2 in detail, Figures 4 and 5 show two R3-232C
6 is a diagram showing a part of the switching circuit of FIG. 2, and FIG. 7 is a diagram showing the connection relationship between interfaces.
The figures are block diagrams showing modified examples. 1...DCE, 2...DTE, 3...Discrimination switching circuit, 10...Discrimination circuit, 11...Switching circuit, 12.
13...R3-232C interface, 29.30
, 31.32... Comparator.

Claims (1)

[Scope of Claims] [1] A device that determines whether an interface is a data termination equipment (DCE) interface or a data terminal equipment (DTE) interface, and includes a voltage comparator connected to a signal line of the interface, The interface determination is characterized in that it is configured to determine whether the interface is the data termination device interface or the data terminal device interface based on a difference in the output of the voltage comparator corresponding to a difference in the voltage level of the signal line. circuit. [2] The purpose is to determine whether the first and second interfaces connected to each other are a DCE interface or a DTE interface, and the transmission data signal line of the first interface and the transmission data of the second interface first and second switches (23) (24) connected in series between the signal line; and one switch connected between the first and second switches (23) (24). a voltage comparator having an input terminal and the other input terminal connected to a reference voltage source, and when determining the first interface, the first interface is connected to determine whether it is a DCE interface or a DTE interface based on a comparison between the reference voltage and the voltage level of the first interface, and when determining the second interface, the second interface is connected. and the second interface is connected to the voltage comparator to determine whether the interface is a DCE interface or a DTE interface based on a comparison between the reference voltage and the voltage level of the second interface. Features an interface discrimination circuit.