JPS60121852A - Circuit monitoring circuit - Google Patents

Abstract

PURPOSE:To eliminate hindrance to the communication system operation of a system which allows a communication between terminal devices by inhibiting the transmission of a carrier when the carrier is sent out except in a transmission state. CONSTITUTION:If the carrier is sent out continuously when a terminal device is not in the transmission state owing to trouble, an NOT circuit 11 outputs ''1'' and an AND circuit 12 outputs ''1'', so that a transmission control part 13 detects the trouble of the device. A transmission control part 13 controls a driver 9 to inhibit the transmission of the carrier. When a transmission indication is not sent any more and the carrier is stopped normally, a transmission carrier detection signal from a carrier monitoring part 10 is also stopped, so a signal for stopping the driver 9 is not sent out.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention relates to a system for communicating between a set of terminal devices R.
Piriru I'l□111 Regarding the transmitting section of the Song equipment, carrier waves may be sent to the communication line at times due to a failure in the terminal equipment, etc., or the entire communication system may become inoperable or partially inoperable. This invention relates to a line monitoring circuit that prevents such a situation from occurring.

(b) Prior Art and Problems There are polling methods, time division multiplexing methods, and the like as communication methods for systems that communicate between terminal devices. Also, recently, the C3MA/CD system has been attracting a lot of attention. This C3MA
The general operation of the /CD system will be explained. Figure 1 shows C3MA/
An example of a system configuration using the CD method ('8i system configuration is shown. As shown in FIG. 1), one lotus 6-1=
For example, the terminal device 2 which is connected to the bus 6 and is about to transmit 7 checks whether a carrier wave exists on the bus 6'2.
Terminal device; queues to 3 and starts transmitting. At this time, other terminal devices 4 may start transmitting at the same time, so there may be a collision, but it is ignored. There is a collision for a certain period of time i)
After that, transmission starts and the process of checking for collisions is repeated. If there is a collision, the communication will be terminated.

If a carrier wave continues to be sent out on a communication line due to a failure of a terminal device, the entire terminal device connected to the same line becomes inoperable in the polling method. C S M A /
CI) method makes the entire communication system inoperable,
Furthermore, in the C3MA/CD method, it is not possible to detect which terminal device is out of order. Furthermore, the time division multiplexing method has the drawback of increasing the load on the multiplexing device and reducing the communication speed of other terminal devices.

(C) Object of the Invention The object of the present invention is to eliminate the drawbacks mentioned in 1. In order to monitor the carrier wave transmission, and to
It is an object of the present invention to provide a line monitoring circuit which prevents interference with the operation of a communication system by blocking the transmission of carrier waves, and which is also capable of detecting faulty terminal equipment.

(d) Configuration of the Invention The configuration of the present invention is to provide a transmitting device having a transmission control section and a transmission section that transmits data on a communication line based on a transmission instruction signal from the transmission control section. a detection means for detecting a data transmission operation of the transmission section in the LJ during a period in which a transmission instruction signal is not outputted from the transmission section; and a detection means (G':') for stopping the data transmission operation of the transmission section once 1-1) Q is provided to prevent the carrier wave output from the transmitter from being transmitted to the communication line in the absence of the transmission instruction signal.

(e) Embodiment of the Invention FIG. 2 is a block diagram of a circuit showing an embodiment of the invention. When transmitting data from a terminal device, the transmission control section 13 includes a data transmission section 8, a carrier wave monitoring section 10, and a NOT circuit 11.
A transmission instruction signal is sent to the

The data stored in the buffer 7 is read out by the data transmitter 8 and sent to the line 6 via one liner 9. The carrier wave monitoring unit 10 monitors the output of the data transmitting unit 8 from time to time,
When the carrier wave is sent out from the data transmitter 8, the ΔND circuit 1
2, the first general transmission detection signal is sent out. NOT circuit 11
is sent (to set the output to “0” by the rs instruction number,
The output of the ND circuit 12 remains at 0''.When the end of transmission is detected by detecting the empty state of the buffer 7, etc., the transmission control unit I3 stops sending out the transmission instruction signal.However,
Even if the transmission instruction signal disappears, the data transmission section 8
If the transmitted wave continues to be transmitted, the output of NO7 times 11 will be “1”, so the output of AND circuit 12 will also be “1”.
”, the transmission control unit 13 detects a failure in the device.The transmission control unit 13 detecting the failure controls the driver 9 to prevent the transmission of the carrier wave.When the transmission instruction signal disappears and the carrier wave also stops normally Since the transmitted carrier detection signal υ of the carrier wave monitoring unit 10 is also stopped, the output of the AND circuit]2 is 0.
Therefore, the transmission control unit 13 does not send out a signal to stop the driver 9.

FIG. 3 is a detailed block diagram of the transmission monitoring section 10. As shown in FIG. The output of the data transmitter 8 enters the level converter 14, which detects the difference in carrier waves and sends a rectangular wave to the terminal 1' of the JK flip-flop 15. , the terminal J of the JK Frisopf 1 tip 15 is set to 1'', and the terminal Q of αiii T- is set to 0'', so the terminal Q is set to 1''. This signal of "P I'" becomes a transmission 1 general transmission detection signal and is sent to the AND circuit 12. A transmission instruction signal is sent from the transmission control section 13 to the terminal of the D Frinobuf IJ knob 19 and the NOT circuit 18. Clock is input from terminal A, I]
It is available at terminal 'F of flip-flop I9. Therefore, 1] the terminal Q of the flip-flop 19 becomes "1", and the signal of this pin is sent to the NAND circuit I7.

The output of the NOT circuit 18 is determined by the transmission instruction signal.

”, so the output of the NAND circuit 17 +4. ” 1
When the transmission is completed, the transmission instruction signal from the transmission control section 13 disappears, and the output from the NOT circuit 18 becomes 1. Then, the terminal of the D flip-flop.

If it is delayed by a time determined by the clock timing, it becomes "0".The output of the NΔAND circuit 17 is the delay time of the D flip-flop Mi+':'Child Q's delay time or P0'.
becomes. This 0" becomes the transmission end detection signal, and it goes through the 01? circuit 16 to the reseno 1 of JK Frisobufu 1 Kotup 15.
- supplied as a signal. A signal for forcibly resetting the JK flip-flop 15 to 1- is input from the terminal I3.

(f) Effects of the Invention As explained above, the present invention prevents the transmission of carrier waves that interfere with the operation of the communication system when a carrier wave is being transmitted when the terminal device is not in a transmitting state due to a failure, and prevents the failure terminal from transmitting the carrier wave. It is possible to normally perform communication with devices other than the device, and to detect a faulty terminal device with 1jJ capability.

[Brief explanation of drawings]

Figure 1 shows the communication system J・(
1! 2 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. 3 is a detailed diagram of the carrier wave monitoring section I-J.
This is a diagram. 1.2.3.4.5 is the crystal 1 song device, 7 is the buffer, 8 is the data transmitter, 9 is the l-lime, 10 is the transmission monitoring unit,
]: NJ transmission control unit, 14 is Leher converter, 15.19
is a Flinopf IJ knob.

Claims (1)

[Claims] In a data transmitting device having a transmission control section and a transmission section that transmits data on a communication line based on a transmission instruction signal from the transmission control section, the transmission section during a period in which the transmission instruction signal is not output from the transmission control section. The i;j transmission instruction signal includes a detection means for detecting a data transmission operation, and a means for blocking the data transmission operation of the MiJ transmission unit by a detection signal from the stage 11; If there is no
11- Preventing the carrier wave output from the transmitter in 1iii from being transmitted to the communication line! A line monitoring circuit with ri"1t.