JPH03254224A - Loopback test circuit - Google Patents

Abstract

PURPOSE:To prevent the malfunction of information circulated in the same block repetitively by providing a selector selecting either a loop bit sent from a subsequent transmitter or a loop bit representing no loopback and sending the selected loop back bit to a host transmitter to each transmitter. CONSTITUTION:A selector 14a selecting either a loop bit sent from an adjacent transmitter or a loop bit representing no loopback and sending the selected loop bit to a host transmitter to a transmitter CNEb and the transmitter CNEb for which loopback is instructed by the loop bit allows the selector 14a to select the loop bit representing no loopback and sends the selected loop bit to a loopback side transmitter. That is, the loopback station CNEb does not send a loop bit in a direction of A C but sends a loop bit set to 0 instead in the direction of C. Thus, the circulation of a signal through the same block due to the duplication of the loopback is prevented.

Description

[Detailed Description of the Invention] [Summary of the Invention] Regarding a loopback test circuit for a transmission device inserted into a transmission line, a loopback transmission line is formed in both the device under test and the test device, and information repeatedly circulates in the same section. For the purpose of preventing malfunctions such as terminating or non-terminating devices, in a loopback test circuit in a communication system in which multiple transmission devices that can be configured as terminating devices or non-terminating devices are connected via a transmission path, The loop bit sent from
A selector for selecting one of the loop focus values indicating non-loopback is provided, and in a transmission device that performs loopback when loopback is instructed by the loop bit, the selector is made to select the loop bit with a value indicating non-loopback. The bottom of the tank is so that it is sent out to the transmission device on the return side.

[Industrial application field]

The present invention relates to a loopback test circuit for a transmission device inserted into a transmission path.

Loopback tests are widely used to test the normality/abnormality of transmission lines and transmission equipment. The present invention is designed to prevent the signal from being repeatedly folded back at this time.

[Conventional technology]

CN E (Center Node Equipme)
nt) is one of the transmission devices, and depending on the settings, the terminal device (
It can be a non-terminating device (with a monitoring function) or a non-terminating device (which simply passes the signal through). This device has a loop function (return test function), and when an abnormality occurs in the communication system to which this device is connected, this function is used to identify the location of the failure.

In FIG. 2, CNE, , CNE, is the transmission line 11+, i! ,2
The above transmission device is inserted into the circuit and includes a return signal line 13.11, selectors 11.12, a loop bit "1" detection circuit, and the like.

Now, CNE is the test machine, CNE is the machine under test, and CN
If the transmission line is turned back at Eh, the transmission equipment CNE,
From the side, the transmission line 7!1 is passed through 13 to the transmission device C.
A control signal with the loop pit set to "1" is sent to the NE, and a data bit "1" indicating that the CNE is the loop end is set in the loop end information memory 18 of the CNE. In the control device CNE, the detection circuit 1'6 detects the loop pit "1" sent from the CNE side, and sends an H level signal to the AND gate 20. Furthermore, since the terminal end "'l"° is set in the memory 18, an H level signal is sent from the memory 18 to the AND gate 20, and therefore the gate 20 outputs an H level signal to select the selector 12.14. Switch. This allows it,,l! ,
, j2. A loopback transmission line is constructed.

Note that transmission line 2. ．． 2. is transmission line 1. , l, but here the loop bit transmission line 11s, 1
m as data/signal transmission line II other than loop bits,!
, z are shown separately. Therefore selector 13.1
4 is actually included in selectors 11 and 12.

Transmission device CNE sends test data (main signal and status bits), and transmission device CNEb returns it.
CNE checks this to know whether the transmission line i,,i,, the transmission device (not shown) inserted into this, and the return transmission device CNEb are normal or abnormal (the test equipment does not change without the main signal and ST bit changing If it returns to , it is normal).

[Problem to be solved by the invention]

The purpose of the loop function is to loop back the main signal and status bits sent from the tester to the device under test, and to make sure that their contents are returned to the tester unchanged. There is a problem in that the main signal and status bits that have returned to the test device are looped back and re-sent to the device under test.

That is, when the test device CNE is also set to terminate and the data bit "1" is set in the loop termination information memory 17, an H level signal is sent from the memory 17 to the AND gate 19, and from CNE to CNE. , Herupit (
The detection circuit 15 detects this and sends an H level signal to the AND gate 19, and therefore the AND gate 19 detects this and sends the AND gate 19. The gate 19 generates an H level output and switches the selectors 11 and 13, thereby forming a folded transmission line.

An object of the present invention is to prevent malfunctions in which loopback transmission paths are formed in both the device under test and the test device, and information repeatedly circulates in the same section.

[Means to solve the problem]

As shown in FIG. 1, in the present invention, each transmission device CNE receives a loop pit sent from an adjacent transmission device (on the downstream side in the forward route of the loopback test) and a value indicating non-loopback, which is "0" in this example. A selector 14a is provided to select one of the loop pits and send it to the next (upstream) transmission device.

[Effect]

The problem of information (main signal and ST bit) circulating in a loop between the test station and the station under test can be solved by inverting the loop pit at the return station and transmitting it. That is, in this example, if the loop bit is "0'', the AND gate 19 (
The output of FIG. 2) is at L level, and the selectors 11 to 13 select the normal outbound side and do not select the return side i4, so information circulation is avoided.

[Example] Turnback in a certain TS (Ti■e 5lot) or bus is as follows: ■ The loop bit in the control signal is "1", and ■ The loop termination information in the CNE is set to termination 1. This is performed when the logical product of the two is 1. However, in the conventional circuit configuration shown in FIG.
Since the loop bit is looped back as it is at step b, the loop focus of "l" which instructs loopback returns from the machine under test CNEb to the test machine CNE. Therefore, if the test machine CNE is set at the end of the loop, the returned main signal and control signal are looped back and sent to the machine under test again. In other words, a malfunction occurs in which the signal continues to circle around the same section.

In this respect, as in the present invention, the return station CNE does not pass the loop bit in the loop direction A-C, but instead sends the loop bit set to "0" in the C direction. As a result, the loop bit of the main signal and control signal that has been folded back once is “0”.
I went back and never had to turn back again. Further, in the present invention, only the bridging portion between A and C in the figure is changed, and the fixed "0" bit is selected by the selector 14a only when loopback occurs. As a result, the main signal and OH signal in the non-loop state are preserved.

FIG. 3 shows a specific example of the loop bit sending circuit.

ANDGATE 20 is an integration episode! ALSO8, selector 14
a is the same ALS 157. More specifically, if the output of the detection circuit 16 is as shown in FIG. 4, and the stored contents of the loop end information memo IJ1B are as shown in the same figure, the output C of the selector 14a is as shown in the figure. It becomes like this. That is, if the input A and the memory storage contents are both H, the output C is L; if either is L, the output C is the same as the input.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent malfunctions in which processing for specific control information is performed in a plurality of devices (signals circulating in the same section due to overlapping loopbacks).

[Brief explanation of drawings]

1 is a diagram showing the principle of the present invention, FIG. 2 is a block diagram showing a conventional example, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is an explanatory diagram of the operation of FIG. 3. A block diagram fil showing an embodiment of the present invention! ! I In FIG. 1, CNE is a transmission device, 2. ~14 is a transmission line, 16
18 is a loop end information memory, and 14a and 12 are selectors.

Claims (1)

[Claims] 1. In a loopback test circuit in a communication system in which a plurality of transmission devices that can be configured to be either terminating devices or non-terminating devices are connected via a transmission line, A selector (14a) is provided for selecting either a loop bit with a value indicating non-loopback or a loop bit with a value (“0”) indicating non-loopback. A loopback test circuit characterized in that a loop bit having a value indicating non-loopback is selected and sent to a loopback side transmission device.