Multi-Tech Systems MT2834MR6 instruction

Chapter 5 - Error Correction, Data Compression, and Speed Conversion

5.1Introduction

The MT2834MR6 has intelligent features beyond those of the AT command set described in Chapter 3. This chapter describes high performance features and commands that provide error correction, data compression and speed conversion capabilities. The remainder of this chapter describes these features and the commands that implement them, as well as related commands.

The MT2834MR6’s error correction complies with the ITU-T V.42 standard. V.42 actually uses two error correction protocols: LAP-M and MNP Class 3 & 4. MNP Class 3 & 4 error correction emerged as the industry standard among modem manufacturers over the past decade. It is now in the public domain, and has been implemented in dozens of modem brands with world wide installations in the hundreds of thousands of units. LAP-M error correction is similar to MNP Class 3 & 4.

The MT2834MR6 provides two types of data compression: ITU-T V.42bis and MNP Class 5. V.42bis data compression is newer; it requires concurrent LAP-M error correction. V.42bis is a very efficient data compression technique that can provide up to 4-to-1 compression, depending on the type of data being transmitted. MNP Class 5 data compression requires concurrent MNP Class 3 & 4 error correction. It is an older and more established standard that offers data compression in the 2-to-1 range, which also depends on the type of data being transmitted.

Speed conversion allows the modem to operate at one speed over the telephone lines and another speed at the RS-232 serial port. This allows the computer or terminal to communicate with the modem at a fixed speed of up to 115,200 bps, while the modem operates at various speeds up to 33,600 bps. Speed conversion is vital if data compression is to be effective, since your terminal or computer must send data to the modem at a higher speed than the modem is sending it over the phone line.

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Multi-Tech Systems MT2834MR6 manual Error Correction, Data Compression, and Speed Conversion

Contents

User Guide Revision Date Description Trademarks Contents Registers Warranty & Service Index 116 Introduction Introduction Manual Organization Description FCC Fax Update FCC Regulations for Telephone Line Interconnection Canadian Limitations Notice Technical Specifications 300 bps DiagnosticsBell 103/113 Fax Carrier Power Supply Speed Modem LED IndicatorsBusy Switch Data Rate bps LED State 10 MT2834MR6 Installation Notes Safety Warnings Dialing and Answering Dial-Up Automatic Answering Dial-Up Handshaking Details Call Termination AT Commands Working with AT Commands Modes of Operation Command Structure Command Editing AT Commands Modem baud rate Baud adjustFlow control disabled Serial port baud rate Escape sequence selection Force answer modeAlternate out-of-band escape sequence Go back online Dial Dialing CommandsDefault none = phone number Default R0 Dial Modifier CommandsDefault P Pulse or Tone Dialing Or 4 through 255 seconds International models ATDT1028806127853500 $123456789 Phone Number Memory Commands NdNe Number Linking = 0 or = 1 or Default none T14082345678 P9,T14089876543 Default &F8 Configuration Storage and Recall CommandsDefault &W1 = 0, 8, or AT&F8&W0 AT&W1 defaultATZ AT&F9&W0 Modem Response Result Code Commands Default Default &A0Result Codes and Call Progress Selection Default B0 Online Connection Commands#An Auto Speed Detection Default #A0 DCn AT Command Control = 0 or Default %DC0 CDn Cleardown at Disconnect = 0 or Default &CD0 DTn Dtmf Detection = 0 or Default DT0#Fn Fallback Modes = 0, 1, or Default #F2 Default &P0 Models outside U.K Default &G0 models outside U.KDefault *H0 G2 U.K. models only Default Y0 #T0 disables TCM#T1 enables TCM Issued V.34 Commands Default &D2 RS-232 Interface CommandsDefault &C1 Default &R1 S0 forces DSR high Default &S1Go high again S1 allows DSR to act normally, that is, to follow CD Default &E15 Error Correction and Data Compression CommandsDefault &E1 #Ln Error Correction Modes Default #L0 $En Error Correction at 300 bps = 0 or Default $E0 $An Autoreliable Buffering = 0 or Default $A0$Rn Retransmit Count = 0 or Default $R0 Speed Conversion Commands $SB1200 $SBn Serial Port Baud Rate = speed Default $SB57600$SB300 $SB2400 Immediate Action Commands Rate Renegotiation $EBn Asynchronous Word Length = 0 or Default $EB0 Flow Control CommandsBSn Maximum Reliable Block Size = 0 or Default &BS1 Flow Control Disable Non-Error Correction Mode Flow Control Default &E6Default &E8 Default &E10 Pacing Computer-Initiated Flow Control Default &E13#Xn Number of Xoff Characters Sent = 0 or Default #X0 = 12 or Escape Sequences Remote Configuration Commands Atcr Remote Configuration Escape Sequence Line Probe Commands Diagnostic Commands Registers Registers Default 8 H Default 13 MDefault 10 J Return Character Unit 1 second Time for Carrier Abort TimerDefault 45 North America and International Range 1-255 U.S.A Maximum S11 value is 255 ms 255 units Registers Registers Reading and Assigning S-Register Values Examples of Assigning ValuesExamples of Reading Values AT Commands Affecting S-Registers Error Correction, Data Compression & Speed Conversion Error Correction, Data Compression, and Speed Conversion How V.42 Detects and Corrects Errors Data Compression MNP Classes 2 #L1 Command V.42 Mode Select Command #L1 #L0 Command 3 #L2 Command Autoreliable Mode &E1 Non-Error Correction Mode &E0Reliable Mode &E2 Modes of Operation Flow Control Flow control and pacing Modem-Initiated Flow Control 1 XON/XOFF Flow Control &E5Hardware Flow Control &E4 1 XON/XOFF Pass-Through &E7 Non-Error Correction Mode Flow Control &E10 and &E11Pacing &E13 Hewlett Packard ENQ/ACK Pacing &E9 Modem-Initiated Flow Control 10.1 V.42 Error Correction ModesNon-Error Correction Mode Flow Control 10.3 XON/XOFF Pass-Through Result Codes MNP Error CorrectionLAP-M Error Correction Speed Conversion Baud Adjust $BA Modem Baud Rate $MB Serial Port Baud Rate $SB Maximum Block Size &BS Related CommandsAutoreliable Buffering $A Autoreliable Fallback Character $F 13.5 V.42 Error Correction at 300 bps $E SummaryRetransmit Count $R Testing & Troubleshooting Testing and Troubleshooting Test Procedure Local Analog Loopback Test V.54 Loop Remote Digital Loopback Test V.54 Loop Remote digital loopback test Local Digital Loopback Test V.54 Loop Local digital loopback test Warranty & Service Multi-Tech Systems, Inc. Warranty & Repairs Policies Warranty2 U.S. and Canadian Customers International Customers outside U.S.A. and Canada International Distributors Repair Procedures for U.S. and Canadian Customers Repair Procedures for International CustomersRepairs Technical Support Internet SiteCountry Telephone Appendices Ascii Conversion Chart Appendix a Appendix B Dial Pulses Tone Dial Frequencies Figure B-2. Standard Dtmf frequencies Appendix C Result Code Summary Standard AT Result Codes &Q1 Register Unit Range Default Description Appendix DRegister Summary S34 AT Command Summary Command Values DescriptionAppendix E CDn 100 101 102 103 104 105 RS-232C Interface Specifications Signal Information Negative PositiveAppendix F Functional Description of the RS-232C Signals Transmitted Data TD Pin 2 To modem Test Voltage +V Pin From modem External Transmit Clock XTC Pin To modem Cable and Connector Diagrams Appendix G Appendix H Introduction to MultiTech Escape Methods How to Select an Escape Method Escape Method 1 +++ATCR Registers and Escape Sequence Aborting an Escape Sequence Introduction to Remote Configuration Basic ProcedureSetup Changing the Passwords Changing the Remote Escape Character Index Index 118 119 120 121 122 S000326A