Multi-Tech Systems MT3334HD8 manual RS-232 Interface Commands, Cn Carrier Detect Control

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3 AT Commands

RS-232 Interface Commands

These commands define how an MT3334HD8 modem will use and respond to standard RS-232 signals.

&Cn Carrier Detect Control

n = 0, 1, 2, or 4 Default: &C1

The &C command lets you control the Carrier Detect (CD) signal on the RS-232/V.24 interface. Normally, CD goes high when the modem detects a carrier on the communications link, and drops when it loses the carrier. By using &C, however, you can force the signal to stay high, or to drop momentarily when the remote modem disconnects. (This option is useful with some CBX phone systems and mainframe front ends, which require CD to act in this manner.) You can also force the modem to reset when the CD signal drops.

&C0 forces CD high.

&C1 allows CD to act normally—to go high when the modem detects a carrier, and to drop when it loses the carrier.

&C2 causes CD to drop for one second on disconnect, and then go high again. (If you want to set the drop time to something other than one second, change register S24.)

&C4 resets the modem when CD drops.

&Dn Data Terminal Ready Control

n = 0, 1, 2, or 3 Default: &D2

The Data Terminal Ready (DTR) signal on pin 20 of the RS-232/V.24 interface must be high, or “on,” in order for the modem to operate. A high DTR signal tells the modem that the computer it is connected to is ready to communicate through the modem.

The DTR signal can also be used to cause the modem to reset to its default parameters, as if you had given the modem an ATZ command.

&D0 (or &D) causes the modem to ignore DTR.

&D1 causes the modem to hang up when DTR drops. While DTR is low, the modem accepts commands, but will not dial or auto-answer until DTR goes high again.

&D2 acts the same as &D1.

&D3 causes the modem to reset when DTR drops . It will also hang up if it is online.

CommPlete Communications Server

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Contents MT3334HD8 Modem User Guide Multi-Tech Systems, Inc Woodale Drive Mounds View, Minnesota CommPlete Communications Server Canadian Limitations Notice FCC Fax WarningTable of Contents Appendix F Testing the MT3334HD8Warranty, Service, and Technical Support Appendix DIntroduction Manual Organization LED IndicatorsPower Supplies IntroductionInstallation Data Rates Modem Technical SpecificationsIntroduction 2400 & 1200 bps MT3334HD8 User Guide Power Installation MT3334HD8 modem card Safety WarningsInstallation Procedure Pre-Installation NotesPage AT Commands Modes of Operation Working with AT CommandsCommand Structure Command Editing AT Commands by Function $BA Continuous Redial Dialing CommandsDial Modifier Commands Ds DialWait for New Dial Tone Pulse or Tone DialingFlash On-Hook Rn Reverse Originate/Answer ModeReturn to Command Mode After Dialing Dialing PauseDsNd Store a Phone Number Phone Number Memory Commands@ Quiet Answer Call Card Tone DetectList Stored Telephone Numbers Configuration Storage and Recall CommandsWn Store Configuration NdNe Number LinkingReset Modem Modem Response Result Code CommandsFn Load Default Configuration Echo Command Mode Characters Result Codes Verbose/Terse Bn Answer Tone Online Connection CommandsAn Answerback #An Auto Speed DetectionDTn Dtmf Detection DCn AT Command ControlCDn Cleardown at Disconnect Pn Set Pulse-Dial Ratios #Fn Fallback ModesGn Guard Tones Hn Busy-Out After Disconnect#Tn Trellis-Coded Modulation RDn Square Wave Ring Detect$Tn Calling Tone RAn Asymmetric Bit Rate CommandsFn Echo Canceler Frequency Offset Compensation Yn Long Space DisconnectDn Data Terminal Ready Control RS-232 Interface CommandsCn Carrier Detect Control SFn DSR/CD Interaction Control Rn Clear to Send ControlSn Data Set Ready Control RFn CTS/RTS Interaction ControlEn Data Compression Error Correction and Data Compression CommandsEn Error Correction Modes #Ln V.42 Error Correction Modes$An Auto-Reliable Buffering $En V.42 Error Correction at 300 bps$Fn Auto-Reliable Fallback Character Enable/Disable $Rn Retransmit Count Speed Conversion Commands$BAn Baud Adjust $SBn Serial Port Baud Rate $MBn Modem Baud RateL5, L7 List Current Operating Parameters Immediate Action CommandsRepeat Last Command Inquire Product CodeFlow Control Commands E5 XON/XOFF Flow Control E3 Flow Control DisableEn Non-Error Correction Mode Flow Control E4 Hardware Flow Control#Xn Number of Xoff Characters Sent En Pacing Computer-Initiated Flow ControlBreakatcr Out-of-Band Escape Sequence Force Answer ModeEscape Sequences +++ATCR In-Band Escape SequenceGo Back Online Remote Configuration CommandsAtcr Remote Configuration Escape Sequence #Ixxxxxx Change Login PasswordDFn Format Line Probe Data Line Probe Commands#Syyyyyy Change Setup Password DPn Read Line Probe DataLn Display Line Probe Data Diagnostic CommandsTn Respond to Remote Digital Loopback Signal RP Immediate Line ProbeUn Loopback Test Modes MT3334HD8 User Guide Registers S2 Escape Code Character RegistersS0 Number of Rings Until Modem Answers S1 Ring CountS6 Wait Time for Dial Tone S7 Time for Carrier Abort TimerS4 Line Feed Character S5 Backspace CharacterS11 Tone Dialing Spacing and Duration S10 Carrier Loss Disconnect Delay TimeS13 Remote Configuration Escape Character S9 Carrier Detect Response TimeS25 DTR Dropout Time S30 Inactivity TimerS34 Command Buffer Length After Online Escape Sequence S24 PBX/CBX Disconnect Drop Time for DSR/CTS/CDS48 Maximum V.34 Connect Speed S94 Out-of-Service TimeS37 DTR Busy-In Time S43 Force V.34 Connect SpeedExamples of Reading Values AT Commands that Affect S-RegistersReading and Assigning S-Register Values Examples of Assigning ValuesAT&E2$SP1#L3$R0$MB19200$SB115200$EB1S0=10&W0CR Testing the MT3334HD8 Local Analog Loopback Test V.54 Loop Test procedureRemote Digital Loopback Test V.54 Loop Testing the MT3334HD8Dial the remote modem and establish your online connection Local digital loopback test Local Digital Loopback Test V.54 LoopPage Warranty, Service, and Technical Support Service Limited WarrantyRecording Product Information Technical SupportDownloading a File Multi-Tech BBSLogging onto the Multi-Tech BBS Bulletins About CompuServeReading a Message Leaving a MessageAbout the Internet About the Multi-Tech Fax-Back ServiceUpgrading the MT3334HD8 Firmware Using FlashPro to Upgrade FirmwareMT3334HD8 User Guide Appendixes Ctrl Code HEX DEC Appendix a Ascii Conversion ChartTone Dial Frequencies Appendix B Dial Pulses and TonesDial Pulses Figure B-2. Standard Dtmf frequencies Multi-Tech Result Codes &Q0 Appendix C Result Code SummaryStandard AT Result Codes &Q1 Appendix D S-Register Summary Register Unit Range Default DescriptionSets fixed V.34 connect speed = 28800 bps Return Appendix E AT Command SummaryCDn AT Command Summary $Fn Command Values Description Command Values Description $MBn RAn Command Values Description SFn Command Values Description #Vn Breakatcr Setup Appendix F Remote ConfigurationBasic Procedure Changing the Remote Escape Character Changing the PasswordsIndex MT3334HD8 User Guide Index Long space break Pacing, 36, 37, 38 enable/disable, 38 ENQ/ACK Commands Loopback tests, 42, 43, 54, 56 tone detection