JPH02105652A - Line terminating equipment - Google Patents

Abstract

PURPOSE:To heighten the applicability of a line terminating set (DCE) by constituting the equipment so as to be able to neglect the communication request of a desired data terminal equipment(DTE) by a command from the outside. CONSTITUTION:SW1 and SW2 are provided with a function to instruct to validate or not the communication requests of DTE interfaces 101 and 102 to a DTE interface selection circuit 11. The communication request of the DTE can be nullified transiently only by adding a simple AND circuit which receives an external signal to recognize whether or not the communication request is effective corresponding to the DTE connected in such a manner. Therefore, when the communication request with high emergency and high priority is issued from a specific DTE, communication can be performed by issuing an instruction to neglect the communication request of another DTE to the DTE.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line terminating device used for data communication in an information processing system, and particularly to a line terminating device located between a data terminal device and a communication line, and used to terminate signals between the data terminal device and the communication line. This relates to a line termination device that performs conversion.

藺米 連 韮) Multiple data terminal equipment (hereinafter abbreviated as DTE) share one line terminating equipment (hereinafter abbreviated as DCE) and one communication line, and the time periods used by each DTE are divided. When data communication is to be performed using a conventional method, there is a method shown in FIG. 6 as a conventional technique.

In FIG. 6, 1 is a DCE, and this DCEl and a plurality of DTEs 21, 22, -=2n are interfaces 101, 102, . . . corresponding to each DTE.
10n. DCEI is n DTs
One of the interfaces with B is selected by the selection circuit 11 at a time and connected to the signal conversion circuit 12 via the internal interface 110.

The signal conversion circuit 12 is connected to a communication line via an interface 120. Inter7z-s 101, 10
2. Old... 1on complies with JIS Cf3361, and no special signals are added to share the communication line.

The selection circuit 11 receives the data terminal ready signal or data set line connection signal (JIS C6
Circuit number 108/1 or 108 specified in 361
/2), it learns the communication request of each DTE, selects only one DTE at a time from among the plurality of DTPs that have requested communication, and connects it to the signal conversion circuit 12 to enable communication.

In the conventional DCB described above, if one DTB attempts to perform high-urgency communication with priority over other DTEs, it either operates the other DTE to stop the communication, or connects the other DTB and DCE. The disadvantage is that the attached cable must be removed. Also, a certain DTE
If a DTE keeps issuing a communication request for a long time due to a failure or the like, other DTEs become unable to communicate, and the faulty DTB must be physically separated from the DCB.

SUMMARY OF THE INVENTION An object of the present invention is to provide a line termination device that can easily invalidate a communication request of a desired DTE simply by external control.

According to the present invention, a plurality of interfaces respectively corresponding to a plurality of data terminal devices, an interface with one communication line, and communication in response to a communication request generated from the data terminal device. A line terminating device having a selection means for selecting a unique data terminal device from among a plurality of data terminal devices that have requested communication and granting communication rights to the data terminal device, the line termination device having a selection means for selecting a unique data terminal device from among a plurality of data terminal devices that have requested communication, and providing communication rights from the data terminal device instructed by an external input signal. A line termination device is obtained which is characterized by having a control means for controlling requests to be invalidated.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the invention.

1.11, 12, 21.22 in this figure.・・・・・・、
2n, 101, 102, ..., Ion
, 110 and 120 are exactly the same as those in FIG. 6 used to explain the prior art. 13 is external signal group 13
0, each DTE21, 22 . . . . , a signal 140 for determining whether to ignore the communication request of 2n, 1
This is a determination circuit that generates 41, . . . , 14n.

FIG. 2 is a specific circuit block diagram of an embodiment of the present invention. In this embodiment, in order to simplify the explanation, a DCB having two interfaces with the DTE is shown. In FIG. 2, reference numeral 11 is a DTE interface. The selection circuit 12 is a signal conversion circuit. The signal group connecting these two circuits 11 and 12, the DTE interfaces 101 and 102, are JIS
Since it is equivalent to the signal specified in C6361, the explanation will be omitted.

The DTE interface selection circuit 11 is the receiving circuit 201
, 203, transmitting circuits 202, 204, and inverting circuit 2
05, AND circuits 206, 208, 209, and a flip-flow 71 circuit 207. The outputs of the receiving circuit 201 and transmitting circuit 202 for the DTE interface 101 are valid only when the output signal 5EL1 of the 79717071 circuit 207 is on (1). Further, the outputs of the receiving circuit 203 and the transmitting circuit 204 for the DTE interface 102 are valid only when the output signal SE[2 of the flip-flop 71 circuit 207 is on (1).

5EL1 and S[[2 are configured so that when one is on, the other is always off.0 The signal ER1 in the figure is
ER2 has data terminal ready/data set line connections (JIS C) for DTE interfaces 101 and 102, respectively.
Line numbers 108/1 and 108/ specified in 6361
2) Shows a signal.

Switches st+i and s%42 are “1” when on,
When off, 0'' is supplied to each input of the AND circuits 208 and 209.

When the input terminal S of the flip-flop circuit 207 is on, the output terminal 01 is turned on and the output terminal Q2 is turned off. Also, when both input terminals S and R are off, output terminal 01 is off, and Q2
is turned on. The correspondence between the states of the input and output terminals is the fourth
See figure, therefore switch S old, 3142
is on, the signal ER1.

The relationship between ER2 and signals 5EL1 and 5EL2 is shown in circuit 205.
, 206.

Due to the action of 207, it becomes as shown in Fig. 5. The time chart will be as shown in Figure 3. In addition, in Figures 4 and 5,
-” indicates that the previous state is retained, and “1”
It is assumed that "0" indicates on and "0" indicates off.

The operation of this embodiment will be explained along the time chart of FIG. At point A of the third tffl, the signals ERI and ER2
Since both are off, both input terminals S and R of the circuit 207 are off, output terminal Q1 is off and output terminal Q2 is on.

Therefore, since the signal output [1 is on and 5EL2 is off, the outputs of circuits 201 and 202 are valid, and the circuit 203゜2
04 output is invalid and DTE interface 101
is connected to the signal conversion circuit 1112.

At point B, the states of signals 5EL1 and 5EL2 do not change.

The signal ERI is turned on and the DTE interface 101
Indicates that the DTE using has started communication.

At point 0, the signal EI12 is turned on, indicating that the DTE using the DTE interface 102 is about to start communication. At this time, both the signals ER1 and ER2 are on, and as shown in FIG. 5, the signal 5EL1.

5EL2 retains its previous state. In other words, the OFF[1 is on, 5EL2 is off, and the DTE interface 102
is disconnected from the signal conversion circuit 12, and communication cannot be performed via this ink face.

In this way, at point B, the started DTE interface 10
Communication via the circuit 204 is not affected by the operation of the DTE interface 102, and even if the DTE using the DTE interface 102 turns on the signal ER2, all output signals of the circuit 204 are in an invalid state.
By checking the signal of circuit number 207 (data set ready) defined in ISC6361, it can be determined that communication cannot be started.

At point D, communication via the DTE interface 101 ends and the signal ER1 is turned off. At this time, the signal ER2 remains on on the DTE interface 102 side,
As shown in FIG. 5, the signal SE1 is turned off and the signal S[[2 is turned on. Therefore, the DTE interface 102 is connected to the signal conversion circuit 12.

Hereinafter, in FIG. 3, the DTE interface 101 is used at points E to F, and the DTE interface 1 is used at points F to H.
02 become available for use.

The above is switch SW1. This is the operation when SW2 is in the on state. When SWl is off, the AND circuit 208
The output of is turned off regardless of whether the signal ER1 is on or off.

Similarly, when SW2 is off, the output of AND circuit 209 is always off regardless of whether signal ER2 is on or off.

As described above, the SW2 has a plow that instructs the DTE interface return circuit 11 whether or not to enable the communication requests of the DTE interfaces 101 and 102.

In this way, each DTE receives an external signal indicating whether or not the communication request is recognized as valid, corresponding to the connected DTE.
DTH communication requests can be temporarily disabled by simply adding a simple AND circuit that forcibly turns off the interface signal data terminal ready/data set line connection with E.

Therefore, when a certain DTE has a communication request with high urgency and priority, the DCE is instructed to ignore the communication requests of other DTEs, and communication is possible by monopolizing the communication line. In addition, if a failure occurs in a DTE and communication requests continue to be issued but do not recover, and other DTBs become unable to communicate, an external source of failure may be caused to the DTE.
It becomes possible to ignore TE's communication requests.

According to the present invention, the communication request of a desired DTE can be ignored by an external command, so that
The dedicated state of the DTH communication line can be controlled according to the occurrence of a DTP failure, the urgency of the DTP, and the priority of the DTP.
This has the effect of improving the operability of CE.

[Brief explanation of the drawing]

Fig. 1 is a system block diagram of an embodiment of the present invention, Fig. 2 is a specific circuit block diagram of an embodiment of the invention, Fig. 3 is a time chart showing the operation of the embodiment, and Fig. 4 is a flip-flow 71 circuit. Figure 5 showing a truth table showing the function of 207
The figure shows the relationship between signals ER1, ER2, 5EL1 and 5EL2, and FIG. 6 is a system block diagram of a conventional line termination device. Explanation of symbols of main parts 1...DCE 11...Selection circuit 13...Judgment circuits 21 to 2n...DTE

Claims (1)

[Claims] (1) A plurality of interfaces respectively corresponding to a plurality of data terminal devices and an interface with one communication line;
A line terminating device having a selection means for selecting a unique data terminal device from among a plurality of data terminal devices that have requested communication and granting communication rights in response to a communication request generated from the data terminal device. What is claimed is: 1. A line termination device comprising: control means for disabling a communication request from a data terminal device instructed by an external input signal.