KR950004207B1 - Interface circuit - Google Patents

Abstract

The circuit automatically processes the switching and specification of control signal according to the interface signal; RTS (Request To Send), CTS (Clear To Send), DTR (Data Terminal Ready), DSR (Data Set Ready). The circuit includes a level conversion means (1) which converts interface control signal level into the cable level-TTL level, a RTS switching menas (2) which controls RTS transmission, a RTS recording means (3) which saves the RTS usage, a CTS switchng means (4), a DTS switchng means (5), a DTR recording means (6), a DSR switching means (7) which controls DSR transmission, and a central processing unit(8) which controls switching actions by the decision of RTS and DTR signals.

Description

Interface circuit of digital terminal equipment

1 is a conventional digital terminal interface circuit diagram.

2 is a block diagram of a digital terminal interface according to the present invention.

3A to 3D are signal timing diagrams for explaining the operation of the present invention.

4 is a flow chart for explaining the operation of the central processing unit (8) in the present invention.

* Explanation of symbols for the main parts of the drawings

1: level converting means 2: RTS switching means

3: RTS recording means 4: CTS switching means

5: DTR switching means 6: DTR recording means

7: DSR switching means 8: Central processing unit, SW0: Automatic setting switch

According to the present invention, a control signal is set according to whether a control signal of a digital terminal device is used, that is, a request to send (RTS), a clear to send (CTS), a data terminal ready (DTR), and a data set ready (DSR) interface signal. A digital terminal equipment (DTE) interface circuit for automatically handling switching.

Conventionally, as shown in FIG. 1, the DCE user operates the switches SW1 to SW4 to set their own state according to whether the interface signal between the digital terminal device and the digital communication equipment (DCE) is used. You should. That is, the signal not used in the control signal is to switch the switch to the normally on contact (NC) side, and the signal used is connected to the corresponding signal line side to selectively control the input to the DCE. For example, when the user terminal device uses RTS and CTS but does not use DTR and DSR, the switches SW1 and SW2 switch to the signal line side so that the RTS and CTS are input to the DCE under the control of the user terminal device. (SW3, SW4) sets the control signal of the DTE by forcibly holding it to the ON contact NC side inside the DCE. However, according to such a conventional interface circuit, if the control signal (RTS, CTS, DTR, DSR) of the DCE is not correctly recognized, a transmission error is frequently caused by incorrectly setting the switches SW1 to SW4. There was a problem. In addition, conventionally, when the DTE does not use the DTR signal, the DCE incorrectly recognizes the failure or failure of the DTE and causes a problem in data transmission.

Accordingly, an object of the present invention is to automatically determine whether to use the DTE interface signal in consideration of the problems of the prior art, and to prevent the occurrence of transmission errors and the failure of data transmission by the DCE automatically performs the initial setting of the interface according to the determination result. It is in removing the factor.

2 shows a digital terminal device interface circuit configuration according to the present invention, which converts the level of the interface signals (RTS, CTS, DTR, DSR) into a gable level-TTL level between the DTE and the DCE. (1), an RTS switching means (2) for controlling whether the RTS is normally turned on or transmitted, an RTS recording means (3) for storing whether the RTS is used, and a CTS for controlling whether the CTS is normally turned on or transmitted Controlling the switching means 4, the DTR switching means 5 for controlling whether the DTR is normally turned on or transmitted, the DTR recording means 6 for storing whether the DTR is used, and whether the DSR is normally turned on or transmitted. Recording and use of the RTS limit DTR according to the DSR switching means 7, the automatic setting switch SW0 for selecting whether to automatically set the interface signal, and the on / off of the automatic setting switch SW0. Judging from the judgment results In this figure, reference numerals 101 to 104 denote NAND gates, 201, 401, 501, 701 AND gates, 301 and 601 delay circuits, and 302, respectively. 602 is a D flip-flop.

Referring to the operation of the present invention made as described above with reference to Figures 2 to 4 as follows.

First, in FIG. 2, the level converting means 1 performs signal level conversion of RTS, CTS, DTR, and DSR from a signal level of a cable connecting between a DTE and a DCE to a TTL level capable of logic processing.

On the other hand, when the automatic setting switch SW0 is turned off, the central processing unit 8 receives a high signal at the output terminals P1, P4, P5, and P8 by a signal supplied to the input terminal P9 of the central processing unit 8. RTS switching means (2), CTS switching means (4), DTR switching means (5), DSR switching means (7) by connecting the interface signal to the normal on-state. When the automatic setting switch SW0 is turned on, the output stages P3 and P7 of the central processing unit 8 are supplied by a signal supplied to the input terminal P9 of the central processing unit 8 as shown in FIG. Output a clear signal (see (C) in Figure 3).

Therefore, since the D flip-flops 302 and 602 are cleared, their high signals are output from the inverted output stage Q thereof as shown in FIG. Supplied to. Subsequently, the central processing unit 8 waits for a predetermined time and then decodes the output Q signal state of the D flip-flops 302 and 602. At this time, the waiting time is to secure a spare time in which the RTS and the DTR can be recorded in the recording means 3 and 6, respectively. In this case, when RTS or DTR is input to the RTS recording means 3 or the DTR recording means 6 as shown in the third simulation (a), the signal is delayed by the delay circuits 301 and 601 for a predetermined time t. Is delayed and supplied to the clock input terminal CLK of the D flip-flops 302 and 602 at the timing shown in FIG. The supplied RTS or DTR (see Fig. 3A) is latched. Therefore, the low signal is output from the output terminal Q of the D flip-flops 302 and 602 as shown in (d) of FIG.

Therefore, the central processing unit 8 decodes the recording state of the RTS recording means 3 and the RTS recording means 6, and determines that the state is to be used when it is low, and when not to use when it is high. In the case of using the result of determination, a high signal is output from the output terminals P1 and P5 to turn on the switching means 2 and 5 so as to be connected to the DTE in a normal state. By outputting a low signal, the switching means 2 and 5 are forcibly turned on (the outputs of the AND gates 201 and 501 are normally low) to be connected to the DCE and the DTE.

As described above, even when the DCE user of the present invention does not exactly know the interface of the used DTE, the DCE can be precisely interfaced to the used DTE, and when a plurality of DCEs are set up in the DTE It is possible to automatically set up according to each DCE / DTE status, so that the accuracy of data transmission and convenience for device installation and operation can be achieved.

Claims (1)

Level converting means (1) for converting the level of the interface control signals (RTS, CTS, DTR, DSR) to the cable level-TTL level between the digital terminal device (DTE) and the digital communication device (DCE), An RTS switching means (2) for controlling whether it is on or transmitting, an RTS recording means (3) for storing whether the RTS is used, a CTS switching means (4) for controlling whether the CTS is normally on or transmitted, and a DTR DTR switching means (5) for controlling whether or not the normal ON or transmission of the DTR recording means (6) for storing the use of the DTR, DSR switching means (7) for controlling the normal temperature or transmission of the DSR and The automatic setting switch SW0 for selecting whether to automatically set the interface signal and the on / off of the automatic setting switch SW0 determine the recording and use of the RTS and the DTR, Central processing station for switching control of signals An interface circuit of a digital terminal device having a tooth (8).