JPH10322418A - Modem, its test control method and test system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a highly reliable test by preventing an output of a loopback signal for a period from start of a local loopback test till the end of on-pattern of pseudo carrier OFF so as to prevent mismatching of data collation just after loop forming. SOLUTION: Upon the detection of an on-pattern by a pseudo carrier pattern detection section 109, the section 109 gives an instruction of setting ON of a CD signal to a carrier detection adjustment section 108. Since the CD signal is set at this point of time, the carrier detection adjustment 108 once resets the CD signal and sets it again at the end of the on-pattern. When the CD signal is reset, a CS-CD detection section 111 raises a detection signal S2, and a CD-OFF detection section 110 outputs a detection signal S1 to a reception data adjustment section 106. When the CD signal is set, the CD-OFF detection section 110 descends the detection signal S1. The reception data adjustment section 106 receiving the detection signals S1-S3 always clamps an RD signal to be binary '1'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modem for data communication (hereinafter referred to as a modem), and more particularly to a local loopback test in which a transmission signal is looped back on its own line side and an error is observed. The present invention relates to a modem and a test control method thereof.

[0002]

2. Description of the Related Art Generally, ITU-
T Recommendation V. 54 is adopted. V. Four types of loops are defined in the loop 54. Among them, there is a loop test called a LALB (local analog loopback) test in which a transmission signal is looped back on the line side of the own station. A modem capable of performing such a self-test is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-246576.

[0003]

However, according to the above-mentioned conventional method of controlling a modem, the method described in ITU-T recommendation V. If the LALB test is started during data communication in the pseudo carrier control mode according to the 13 regulations, the following problem occurs. That is, when the LALB test is started for some reason during data communication in the pseudo carrier control mode setting, the transmission unit (here, the modulation unit) is formed to form a loop in the own station.
The training signal and the on-pattern for pseudo carrier control transmitted from the receiver are input to a receiver (here, a demodulator).
It is output to the terminal as D (received data). For this reason, a mismatch occurs in the data collation immediately after the loop is formed,
An effective test cannot be performed, and a system error may occur.

An object of the present invention is to provide a modem, a test control method and a test system for the same, which can prevent a mismatch in data collation immediately after loop formation and enable a highly reliable test.

[0005]

SUMMARY OF THE INVENTION A modem and a method of controlling the same according to the present invention, when a local loopback test is started in a state where the pseudo carrier control mode is set, a pseudo loop is started from the start of the local loopback test. It is characterized in that the output of the loopback signal is prevented until the on-pattern of the carrier control is completed.

Thus, even when the LALB test is started during data communication in the pseudo carrier control mode setting, the output of the received data as the loopback signal can be prevented during the period from immediately after the start to the end of the ON pattern. In addition, it is possible to prevent the terminal device from receiving a training signal or an ON pattern generated immediately after the activation. Therefore,
It is possible to avoid inconsistency in data collation immediately after the loop is formed, and to perform data collation after the elapse of this period, thereby executing a highly reliable test.

[0007]

FIG. 1 is a block diagram showing an embodiment of a modem according to the present invention. The modem according to the present embodiment is connected between a data terminal device (not shown) such as a computer and a communication line such as a telephone line. The modem is connected to the terminal device by, for example, the terminal interface unit 101 of RS232C, and receives an RS (transmission request) signal, a CS (transmission enabled) signal, a CD (carrier detection) signal, and reception data (R
D), transmission data (SD), serious indication (TI) signals, and the like are input and output to and from the terminal device. Further, the terminal interface unit 101 can generate a control signal supplied to the inside of the modem at the time of a loop test, as described later.

The SD signal (transmission data) from the terminal interface unit 101 is transmitted to the pseudo carrier pattern adding unit 10.
2 to the modulator 103. The pseudo carrier pattern adding unit 102 is active only when the pseudo carrier control mode is set. More specifically, the RS signal is OF
In the case of F, the SD from the terminal interface unit 101
An idle pattern for pseudo carrier control is added to the signal, and when the RS signal is ON or the CS signal is ON, an ON pattern for pseudo carrier control is added and transmitted to the modulation section 103.

[0009] Modulating section 103 modulates the carrier according to the SD signal input through pseudo carrier pattern adding section 102 and transmits the modulated signal to the communication line through folding section 104. The folding unit 104 normally connects the modulation unit 103 and the demodulation unit 105 to the communication line, but switches the connection during a loop test to output the output of the modulation unit 103 to the demodulation unit 10.
Return to the input of 5.

[0010] Demodulation section 105 demodulates the signal input from folding section 104, and performs RD through reception data adjustment section 106.
The signal is output to the terminal interface unit 101 as a signal. The carrier detection unit 107 detects a carrier from the signal input from the folding unit 104, and if detected, converts the CD signal into an O signal.
N is output to the carrier detection adjustment unit 108. Also,
The pseudo carrier pattern detection unit 109 detects an idle pattern and an ON pattern from the output of the demodulation unit 105, and controls the carrier detection adjustment unit 108 according to which one has been detected. More specifically, the pseudo carrier pattern detection unit 109 instructs the carrier detection adjustment unit 108 to turn off the CD signal when detecting an idle pattern, and turns on the CD signal when detecting an on pattern. To instruct. That is, the carrier detection adjustment unit 108
Generates a CD signal by adjusting the output of the carrier detection 107 in accordance with the output of the pseudo carrier pattern detection unit 109, and outputs the CD signal to the terminal interface unit 101. The CD signal output from carrier detection adjustment section 108 is C
It is also output to the D-OFF detection unit 110 and the CS-CD detection unit 111.

The CD-OFF detector 110 detects that the CD signal is O
If it is FF, the detection signal S1
Output to 6. The CS-CD detection unit 111 inputs a CS signal from the terminal interface unit 101 in addition to the CD signal,
After the CS signal is turned on after the LALB test starts, CD
It detects the time until the signal is turned off and outputs a detection signal S2 to the reception data adjustment unit 106. Also, CS-OF
The F detection unit 112 receives CS from the terminal interface unit 101
The signal is input, and when the CS signal is OFF, the detection signal S3 is output to the reception data adjustment unit 106.

The reception data adjustment unit 106 receives the detection signals S1 to S3 and adjusts reception data. More specifically, while these detection signals S1 to S3 are being input, a predetermined binary “1” signal (Z pattern) is output to the terminal interface unit 101 as an RD signal and transmitted to the terminal device side. As will be described later, when the LALB test is started, the RD signal is clamped in the Z pattern during a period from when the CS signal is turned OFF to when the CD signal is turned from OFF to ON. In other words, the terminal device does not receive the received data during that period.

The loop test control unit 113 switches the loopback unit 104 to form a loop when starting the LALB test, and at the same time, controls the terminal interface unit 101 as described below to control the LALB test. The operation of the entire modem is controlled by a control unit (not shown).

FIG. 2 is a timing chart showing an embodiment of a method for controlling a test of a modem according to the present invention. Normal,
The modem is set to pseudo carrier control mode,
When the LALB test is started during data communication with this setting, the loop test control unit 113 controls the loopback unit 104 and the terminal interface unit 101 to form a loop.
Since the RS signal from the terminal device is ON during data communication, the loop test control unit 113 controls the terminal interface unit 101 to turn off the internal RS. After confirming that the CS signal was turned off,
Turn on the internal RS. When the internal RS is turned on, the modulation unit 103 sends out a training signal until the CS signal is turned on, and the training signal is input to the demodulation unit 105 through the loopback unit 104.

When the CS signal is turned off, C
The S-OFF detection unit 112 outputs the detection signal S3 to the reception data adjustment unit 106, whereby the reception data adjustment unit 1
06 clamps the RD signal to a binary "1" Z pattern.

When the transmission of the training signal is completed and the CS signal is turned on, the pseudo carrier pattern adding section 102
Sends the ON pattern of the pseudo carrier control to the modulation section 103. At the same time, when the CS signal is turned on, CS-OF
The F detection unit 112 lowers the detection signal S3 and outputs the CS-CD
The detection unit 111 converts the detection signal S2 into the reception data adjustment unit 106
Output to

When the pseudo carrier pattern detecting section 109 detects the ON pattern, the pseudo carrier pattern detecting section 109 sends a C signal to the carrier detecting and adjusting section 108.
Instructs to turn on the D signal. At this point, since the CD signal is ON, the carrier detection adjustment unit 108 temporarily turns the CD signal OFF and turns it ON at the end of the ON pattern. When the CD signal is turned off, the CS-CD detector 1
11 falls the detection signal S2, and the CD-OFF detection unit 1
10 outputs the detection signal S1 to the reception data adjustment unit 106. Then, when the CD signal is turned on, the CD-OFF
The detector 110 falls the detection signal S1. As described above, while the detection signals S1 to S3 are being input, the reception data adjustment unit 106 always clamps the RD signal to the binary “1” signal (Z pattern). Since this Z pattern means “no received data” for the terminal device, after all, L
The RD signal is not sent to the terminal device from the time when the ALB test is started and the CS signal is turned OFF to the time when the CD signal is turned ON.

When the CD signal is turned on, the loop test control section 113 sends a test display signal (TI) from the terminal interface section 101 to the terminal device. Thus, the LALB test of the modem by the terminal device is started. That is, the terminal device transmits predetermined test data to the terminal interface unit 10.
1 to the modem, and the SD signal
It returns at 04 and returns to the terminal device again. The terminal device checks the modem by comparing the transmitted test data with the data returned from the modem.

As described above, even if the LALB test is started during data communication in the pseudo carrier control mode setting, the training is performed to invalidate the received data during the period from the start to the start of the CD signal. It is possible to prevent a situation in which the terminal device receives a signal or an ON pattern of pseudo carrier control.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a modem according to the present invention.

FIG. 2 is a timing chart showing an embodiment of a test control method for a modem according to the present invention.

[Explanation of symbols]

 Reference Signs List 101 terminal interface unit 102 pseudo carrier pattern adding unit 103 modulation unit 104 folding unit 105 demodulation unit 106 received data adjustment unit 107 carrier detection unit 108 carrier detection adjustment unit 109 pseudo carrier pattern detection unit 110 CD-OFF detection unit 111 CS-CD detection Unit 112 CS-OFF detection unit 113 Loop test control unit 113

Claims (12)

[Claims] 1. A method of controlling a modem having a local loopback test function, comprising the steps of: starting up the local loopback test when the local loopback test is started in a pseudo carrier control mode.
A test control method for a modem, wherein output of a loop-back signal is prevented during a period from a start of a loop-back test to an end of a pseudo carrier control ON pattern. 2. The modem has a predetermined interface for connecting to a data communication device, and has a transmission enable signal (C
2. The modem test control according to claim 1, wherein the start of the local loopback test is detected by S), and the end of the on-pattern of the pseudo carrier control is detected by a carrier detection signal (CD). Method. 3. The method according to claim 1, wherein the transmission enable signal changes to OFF.
And a second time when the transmission enable signal is changed to ON, and a third time when the carrier detection signal is changed to OFF from the second time when the transmission enable signal is changed to ON. Detecting a fourth time at which the detection signal has changed from OFF to ON to a fourth time at which the detection signal has changed to OFF; and setting a period from the start of the local loopback test to the pseudo time from the first time to the fourth time. 3. The test control method for a modem according to claim 2, wherein the output of the loopback signal is prevented as a period until the end of the ON pattern of the carrier control. 4. The output of the loopback signal is set to binary “1” during a period from the start of the local loopback test to the end of a pseudo carrier control ON pattern. Item 2. A test control method for a modem according to Item 1. 5. A modem having a pseudo carrier control function and a local loop back test function, comprising: an interface means for connecting to a data communication device; and when starting up the local loop back test started in a pseudo carrier control mode. Test start detecting means for detecting the period, a period detecting means for detecting a period from the start of the local loopback test to the end of the on-pattern of the pseudo carrier control, a period detected by the period detecting means, a loopback signal And a data adjusting means for preventing output to the data communication device. 6. The test start detecting means includes a transmission enable signal (C
S), the start of the local loopback test is detected, and the period detecting means detects the carrier detection signal (C
6. The modem according to claim 5, wherein the end of the on-pattern of the pseudo carrier control is detected by D). 7. The apparatus according to claim 1, wherein said period detecting means is turned on from a first time when said transmission enable signal is turned off.
First detecting means for detecting up to a second time at which the signal has been converted to a second time, and second means for detecting from a second time at which the transmission enable signal has changed to ON to a third time at which the carrier detection signal has changed to OFF. Detection means; and third detection means for detecting a fourth time at which the carrier detection signal changes from OFF to ON to a fourth time at which the carrier detection signal changes to ON. 7. The modem according to claim 6, wherein the output of the loopback signal is prevented during a period from the first time to the fourth time according to a detection output of the detection unit. 8. The data adjusting means sets the output of the loopback signal to binary “1” during a period from the start of the local loopback test to the end of the pseudo carrier control ON pattern. Claim 5
The stated modem. 9. A data terminal, a modem connected to the data terminal by a predetermined interface and having a pseudo carrier control function and a local loopback test function,
A modem test system comprising: a transmitting unit for transmitting predetermined data to the modem through the interface; and a collating unit for collating loopback data from the modem with the predetermined data. The modem includes: a test activation detecting unit configured to detect when the local loopback test activated in the pseudo carrier control mode is activated; and a time period from the activation of the local loopback test to the end of the on-pattern of the pseudo carrier control. A modem test system comprising: a period detecting unit for detecting; and a data adjusting unit for not outputting the loopback data to the data communication device during the period detected by the period detecting unit. 10. In the modem, the test start detecting means detects a start of the local loopback test by a transmission enable signal (CS), and the period detecting means detects the pseudo carrier by a carrier detection signal (CD). 10. The modem test system according to claim 9, wherein the end of the control ON pattern is detected. 11. The method according to claim 1, wherein the period detecting means is turned on from a first time when the transmission enable signal is turned off.
First detecting means for detecting up to a second time at which the signal has been converted to a second time, and second means for detecting from a second time at which the transmission enable signal has turned on to a third time at which the carrier detection signal has turned off. Detection means; and third detection means for detecting a fourth time at which the carrier detection signal changes from OFF to ON to a fourth time at which the carrier detection signal changes to ON. 11. The modem test system according to claim 10, wherein output of the loopback signal is prevented during a period from the first time to the fourth time according to a detection output of the detection unit. 12. The modem, wherein the data adjustment unit sets the output of the loopback signal to binary “1” during a period from the start of the local loopback test to the end of a pseudo carrier control ON pattern. The modem test system according to claim 9, wherein: