Multi-Tech Systems BA-Series manual Flow Control Commands, Retransmit Count $R

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MultiModemBA User Guide

Retransmit Count $R

If errors are received during a Reliable connection, the modem re-sends the block of data which contained an error. With the $R0 command, if another error occurs, the block will be re-sent again. The modem counts the number of times that a data block is re-sent. If the same block of data is resent 12 times and still has not been received properly, the modem assumes that the transmission line is unsuitable for transmission, and abort the connection.

This retransmit counter is disabled by the $R1 command. When the retransmit counter is disabled, the modem keeps trying to send data and will not abort, no matter how many times the same block is resent.

AT$R0 = Disconnect if retransmit count is exceeded.

AT$R1 = Do not disconnect due to retransmits.

The factory default setting is $R0.

V.42 Error Correction/300bps $E

At 300 bps, error correction is not typically used. $E1 lets the modem function at 300 bps in either Normal (&E0), Auto-Reliable (&E1) or Reliable (&E2) mode. $E0, which is the modem’s default, disables 300 bps/V.42 error correction altogether.

AT$E0 = No V.42 Error correction at 300 bps.

AT$E1 = V.42 Error Correction at 300 bps.

The factory default setting is $E0.

4.4.9Flow Control Commands

Flow control refers to the techniques used by computer devices to stop and restart the flow of data to and from each other. Flow control is necessary so that a device does not receive more data than it can handle. In the case of the MultiModem, there is a need for flow control in both directions. As illustrated on the next page, flow control for data passing from your computer to the modem is called Modem-Initiated Flow Control and flow control for data passing from the modem to your computer is called Computer/Terminal-Initiated Pacing.

The MultiModem supports both hardware and software Modem Initiated Flow Control. On the Computer/Terminal-Initiated Pacing side, it supports hardware and software flow control, and a special version used by Hewlett-Packard compatible systems called ENQ/ACK Pacing. The modem allows hardware and software pacing to be passed through the modem to the other end of the link so that your computer or terminal can control data start/stop activity through your modem.

This is called Xon/Xoff Pass-Through. To state it simply, “Flow Control” is something the modem does to the computer, while “Pacing” is something the computer does to the modem.

Modem-Initiated Flow Control

Modem

 

RS-232/V.24

 

 

Data Flow

 

 

 

 

 

Computer

or

Terminal

Computer-Initiated Flow Control Pacing

Modem

RS-232/V.24

Data Flow

Computer

or

Terminal

Figure 4-1. Flow Control and Pacing

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Contents User Guide User Guide Record of RevisionsContents Index 106 Introduction and Description How To Use This Manual IntroductionModem Features Callback and Remote ConfigurationDIP-Switches Warranty, Service & Technical Support1 2834 Series Features Fax FeaturesTechnical Specifications Power Modem LED Indicators MT2834 LED DisplayControls on PC Board Installation and Connection What is in Your Modem Package? InstallationSafety Warnings Installation ProcedureInstallation and Connection Step ProcedureInstalling Data Communications Software MultiModemBA/BAI ConnectionsSoftware Configuration and Modem Basics Configuring Your Software Configuring Software for Your ModemPC Initialization Strings AT &F X4 S0=0 MChanging Default Parameters Configuring Software for Your ComputerConfiguring Software for the Remote System Other ParametersTerminal Emulation File Transfer ProtocolsCommand Mode AT Command Editing Functional ModesSummary of AT Commands Command ModeStore Modem Configure Data Multi-Tech Result Codes Result CodesStandard AT Result Codes Dialing Commands Dialing Action Commands Dial Command DContinuous Redial not used in BAI a or Dialing a Stored Number NDial Modifier Commands DTR Dialing $DVoice/Data Dialing $VD Pulse or Tone Dial P TReturn to Command Mode After Dial Command Execution Reverse the Mode of Operation RSet Pulse Dial Ratios &P Automatic Pauses in DialingPhone Number Memory Commands Flash On HookCalling Card Detect Tones $ Quiet Answer @Number Linking NN Configuration and Default Storage CommandsListing Numbers Stored in Memory L Loading Factory Defaults &F Modem Reset ZAsync/Sync Mode Switching &M Unix Uucp Spoofing $SPCommand Response Result Code Commands Echo Command Mode Characters EResult Codes Enable/Disable and No Response Answer Q Result Codes Multi-Tech or Standard AT &QResult Codes Basic and Extended and Call Progress Selection Phone Line Conditioning CommandsGuard Tones Not Used in BAI Models &G Enable/Disable Trelis Coded Modulation #T Fallback Modes When On-Line #FBell/V.21 Tone Phone Line Monitoring Speaker M7 RS-232C Interface Control Commands Enable/Disable Lowspeed Fast Connect $FCCleardown at Disconnect &CD Auto Speed Detect #AData Terminal Ready Control &D CTS Control &RData Set Ready Control &S CTS/RTS Interaction Control &RFError Correction Commands Enable/Disable Auto Reliable Fallback Character $F Auto-Reliable Buffering $AError Correction/300bps $E Flow Control CommandsRetransmit Count $R Xon/Xoff Flow Control &E5 Hardware Flow Control &E4Xon/Xoff Pass-Through &E7 Normal Mode Modem Flow Control On &E11 Send Xon/Xoff Characters #XHewlett-Packard ENQ/ACK Pacing &E9 Terminal/Computer Initiated Pacing &E13Normal/Auto-Reliable/Reliable Mode Commands Xon/Xoff Pass-Through CommandsEnq/Ack Pacing Commands Parity Selection #PSpeed Conversion $BA Speed Conversion CommandsModem Baud Rate $MB Serial Port Baud Rate $SB Immediate Action Commands Force Answer Mode a Off Hook HLine Probe Commands Exiting Command Mode, Going Back On-Line OEnable/Disable Reading of Line Probe Information Commands Format of Line Probe Graph or Table CommandsRegisters Number of Rings Until Modem Answers Rings Which Have OccurredEscape Code Character Return CharacterTime for Carrier Abort Timer Line Feed CharacterBackspace Character Wait Time for Dial ToneS10 Carrier Loss Disconnect Delay Time S13 Remote Configuration Escape CharacterCarrier Detect Response Time S11 Tone Dialing Tone Spacing and DurationS15 Callback Time Delay S16 Callback AttemptsS17 Changing Break Time S24 PBX/CBX Disconnect Drop Time for DSR/CTS/CDS26 Failed Password Attempts S29 Local Inactivity TimerS30 Inactivity Timer S32 Time Elapse for Escape SequenceReading and Assigning S-Register Values S36 Time Between DTR Inactive and Modem Off-HookS37 Time Between DTR Active and Modem On-Hook S48 Program V.34bis Connect Speeds 2834 Series onlyExamples of Assigning Values AT Command and S-Register SummaryExamples of Reading Values Callback Security and Remote Configuration Callback Feature Description Remote Configuration DescriptionTo turn your modems Callback Security feature on and off To change your Remote Configuration feature statusTo set parity of the password/message prompt AT#DB2CR or AT#DB1CR Remote Configuration Procedures Callback Security and Remote ConfigurationCallback Operational Sequence Procedures Remote Configuration Operation Procedures StepProcedureRemote Configuration and Callback Security AT Commands Callback Security Enable/DisableChange Login Password AT#I=yyyyyyyyyyCRRemote Configuration/Callback Security S-Registers Local Inactivity Timer S29 DIP-Switch Settings DIP-Switch Option Settings PC BoardSwitch #4 AS/400 Mode Synchronous Mode/Leased Line/Dial-UP DIP-Switch SettingsMultiModemBA User Guide = Down Down Speaker Volume Control Switch #16 Reserved for Future UseRecording Option Configurations Switch Function Position EffectDIP Switches #13-14 DIP Switches #15-16Warranty, Service and Tech Support Multi-Tech Systems, Inc. Warranty & Repairs Policies Warranty, Service, and Technical SupportOnline Warranty Registration Repair Procedures for International DistributorsReplacement Parts Technical SupportInternet Sites Country TelephoneAppendixes Upgrade Overview Appendix a Upgrading Your Modem’s FirmwareDownload the Upgrade File Upgrade the Modem’s Firmware None of the LEDs Light When the Modem Is On Appendix B TroubleshootingModem Does Not Respond to Commands Appendix B Troubleshooting Modem Dials But Cannot Make a Connection Modem Cannot Connect When Answering Modem Disconnects While On-lineFile Transfer Is Slower Than It Should Be Am Losing DataAm Getting Garbage Characters on the Monitor Appendix C AT Command Summary Apendix C AT Command SummaryCommand Values Description MultiModemBA User Guide Command Values Description SN d$Fn RF n $SBn Break Atcr Callback Security/Remote Configuration Command Summary Command Description #Ixxxxxxxxxx Password Command Summary#Syyyyyyyyyy 25bis Commands Appendix D V.25bis Operation Delayed and Forbidden Numbers25bis Operation 25bis Mode AT Commands 25bis DIP-Switches25bis Set-Up and Initialization Appendix D V.25bis Operation25bis AT Commands Enable/Disable V.25bis Mode $V CommandChange Serial Baud Rate CSP Command 25bis Responses Result CodesDial Phone Number Provided CRN Command Listing Delayed Phone Numbers RLD CommandListing Forbidden Phone Number RLF Command Disregard or Connect to Incoming Calls DIC or CIC CommandDTR Dialing $D Command ITU V.25bis Country Specific InformationItaly SwitzerlandAppendix E MultiModemBA Cables Austria FranceBelgium SingaporeAppendix E MultiModemBA Cables Figure E-1. RS232 Cable IBM PCAppendix F Regulatory Information FCC Part FCC Part 68 TelecomAppendix F Regulatory Information Industry CanadaCanadian Limitations Notice 104International Modem Restrictions EMC, Safety, and R&TTE Directive Compliance105 Index 106Index 107PBX/CBX Disconnect Drop Time for DSR/CTS/CD53 108109
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