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Multi-Tech Systems MT2834MR6 6.4 Local Digital Loopback Test (V.54 Loop 2)

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Chapter 6 - Testing and Troubleshooting

6.4 Local Digital Loopback Test (V.54 Loop 2)

This test is identical to the remote digital loopback test with one exception. Instead of using your modem to

signal a remote modem to place itself in digital loopback mode, your modem is placed in digital loopback

mode while the remote modem is not. Data is entered and transmitted from the remote modem, sent across

the phone line to the local modem, and looped back to the remote modem. See Figure 6-3.

Figure 6-3. Local digital loopback test

6.4.1 Test Procedure

1. Open your communications software and go into terminal mode. Type AT and press ENTER; you should

get an

OK

message. Enter AT&E0<CR> to disable error correction.

2. Dial the remote modem and establish your online connection.

3. Type an escape sequence (+++AT<CR> or <BREAK>AT<CR>) to bring your modem into command

mode while still maintaining the connection with the remote modem.

4. Type ATU3 and press ENTER. Once you receive an

OK

message from your modem (if responses are

enabled), your modem is placed in digital loopback mode.

5. Have someone enter data from the remote keyboard. For this test, typing multiple uppercase

U

characters is a good way to send an alternating test pattern of binary ones and zeros. The data received

by your modem enters its analog receiver, is converted to digital data, is reconverted into analog, and

then is transmitted back to the remote modem. Your modem passes this test if the data received on the

remote monitor is the same as the data entered from the remote keyboard.

6. To exit the test, enter an escape sequence (+++AT<CR> or <BREAK>AT<CR>), which returns the

modem to command mode. The modem should respond with an

OK

message. If you wish to stay on line

with the remote modem for normal data transmission, type ATO and press ENTER. If you wish to

terminate the call, type ATH and press ENTER to hang up.

Contents

Main Revision Date Description Contents Page Page Page Page 1.1 Introduction 1.2 Manual Organization 1.3 Description Owners Manual 1.4 FCC Regulations for Telephone Line Interconnection 1.4.1 FCC Fax Update 1.5 Canadian Limitations Notice 1.6 Technical Specifications Page 1.7 Power Supply 1.8 Modem LED Indicators Note: The MultiModemManager can perform the same function using software. 1.9 Busy Switch 1.10 MT2834MR6 Installation Notes Owners Manual Note: Such apparatus may have been approved subject to limitations in its use. 1.11 Safety Warnings Page Chapter 2 - Dialing and Answering 2.1 Introduction 2.2 Dial-Up Automatic Answering 2.3 Dial-Up Handshaking Details Chapter 2 - Dialing and Answering 2.4 Call Termination Page 3.1 Working with AT Commands 3.1.1 Modes of Operation 3.2.2 Command Structure 3.3.3 Command Editing Page Page Page 3.2 Dialing Commands 3.3 Dial Modifier Commands Page Page 3.4 Phone Number Memory Commands Page 3.5 Configuration Storage and Recall Commands Page 3.6 Modem Response (Result Code) Commands Page 3.7 Online Connection Commands Page Page Page 3.8 V.34 Commands 3.9 RS-232 Interface Commands Page 3.10 Error Correction and Data Compression Commands Page 3.11 Speed Conversion Commands Page 3.12 Immediate Action Commands Page 3.12 Flow Control Commands Page Page 3.13 Escape Sequences ATA S7 A 3.14 Remote Configuration Commands 3.15 Line Probe Commands 3.16 Diagnostic Commands Page 4.1 Introduction 4.2 S-Registers Page S7 S8 S10 S9 S9 S11 S11 S25 S24 &C Page Page 4.3 Reading and Assigning S-Register Values 4.3.1 Examples of Assigning Values 4.3.2 Examples of Reading Values 4.4 AT Commands Affecting S-Registers Page 5.1 Introduction 5.2 How V.42 Detects and Corrects Errors detected correction 5.3 Data Compression $BA0 &E5 &E4 $SB115200 #L 5.5 V.42 Mode Select Command ( #Ln #L0 #L 5.6 Modes of Operation &E0 &E1 5.6.3 Autoreliable Mode ( &E2 5.7 Flow Control 5.8 Modem-Initiated Flow Control &E5 &E4 5.8.2 Hardware Flow Control ( 5.8.1 XON/XOFF Flow Control ( &E13 5.9 Pacing ( &E9 5.9.3 Hewlett Packard ENQ/ACK Pacing ( &E11 5.10 Compression, Error Correction, Flow Control, and Pacing Commands 5.11 Result Codes 5.11.1 MNP Error Correction 5.11.2 LAP-M Error Correction 5.11.3 Data Compression 5.12 Speed Conversion $BA 5.12.1 Baud Adjust ( 5.12.2 Modem Baud Rate ($MB) 5.12.3 Serial Port Baud Rate ($SB) 5.13 Related Commands 5.13.1 Autoreliable Buffering ($A) 5.13.2 Maximum Block Size (&BS) 5.13.3 Autoreliable Fallback Character ($F) 5.13.4 Retransmit Count ($R) 5.14 Summary Page 6.1 Introduction Note: Loopback tests operate at all speeds except 300 bps. 6.2 Local Analog Loopback Test (V.54 Loop 3) 6.2.1 Test Procedure CONNECT 6.3 Remote Digital Loopback Test (V.54 Loop 2) 6.3.1 Test Procedure 6.4 Local Digital Loopback Test (V.54 Loop 2) 6.4.1 Test Procedure Page 7.1 Multi-Tech Systems, Inc. Warranty & Repairs Policies 7.1.1 Warranty mtsrepair@multitech.com www.multitech.com www.multitech.com. 7.1.3 International Customers (outside U.S.A. and Canada) 7.1.4 International Distributors 7.2 Repairs 7.2.1 Repair Procedures for U.S. and Canadian Customers 7.2.2 Repair Procedures for International Customers 7.2.3 Repair Procedures for International Distributors 7.2.4 Replacement Parts 7.3 Technical Support 7.4 Internet Site Page Appendix A ASCII Conversion Chart CTRL CODE HEX DEC CODE HEX DEC CODE HEX DEC CODE HEX DEC Appendix B Dial Pulses Tone Dial Frequencies Appendix C Result Code Summary CONNECT R or the letter &Q1 &Q Standard AT Result Codes ( L CONNECT Appendix D S-Register Summary Page Appendix E AT Command Summary Command Values Description Page &En n &E5 %Fn n $Fn n &F Page Page Page Page Page Appendix F RS-232C Interface Specifications Page Test Voltage (+V) Pin 9 (From modem) High Speed (HS) Pin 12 (From modem) Transmit Clock (TC) Pin 15 (From modem) Receive Clock (RC) Pin 17 (From modem) Data Terminal Ready (DTR) Pin 20 (To modem) Page Appendix G Cable and Connector Diagrams APPENDIX H Introduction to MultiTech Escape Methods How to Select an Escape Method Escape Method 1: +++AT<CR> Escape Method 2: <BREAK>AT<CR> S-Registers and Escape Sequence A S34 Aborting an Escape Sequence APPENDIX I Introduction to Remote Configuration Basic Procedure Setup Changing the Passwords Changing the Remote Escape Character Page Index A B C D E F G H I K L P Q R S T V W X