Flow Control, Hardware and software flow control

FLOW CONTROL

	This chapter contains information about
	■ Hardware and software flow control
	■ Received-data flow control
	■ Transmit-data flow control

Overview	The Business Modem has two buffers, one for data transmitted from your
	computer, and one for data received from the phone line.
	Flow control provides a system for stopping and starting transmission
	depending on how full the buffers are. Flow Control’s purpose is to
	prevent overfilling the buffers, which may cause data to be lost.
	We recommend that you use hardware flow control. If you do,
	depending on your communications software, you will also need to
	enable hardware flow control in your communications software.

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3Com 56K manual Flow Control, Hardware and software flow control, Received-data flow control, Transmit-data flow control

Contents

3Com OfficeConnect 56K Business Modem Command Reference United States Government Legend 3Com Corporation 3800 Golf Rd Rolling Meadows, Illinois Contents Making International calls If You Are Using MS-DOSCommand and Online Modes Other Operating Systems Overview Serial Port Rates Connection Rates Result Code Display Commands Additional Result Code SubsetsOverview Data Terminal Ready Data Set Ready Carrier Detect Remote Configuration Setting DTE Rate to 230 KbpsSetting up Dial Security Password Prompting Received Data Flow Control Error ControlMNP Error Control Testing the Business Modem using AT&Tn Testing Using Keyboard Data AT&T6 Digital Loopback Testing AT&T3Remote Digital Loopback Testing AT&T6, AT&T7 Canceling All Digital Loopback Test Requests &T5 Hardware Flow Control Software Flow control No Flow Control Getting New Operating SoftwareSending New Software to your modem If Your Modem Doesn’t Respond Serial Ports Macintosh modem Additional Specifications Serial PortsRegisters Information This Guide About this GuideIntroduction Finding Specific Wait n seconds between losing the connection ConventionsIcon Description Convention Description Related About this Guide Windows 95/98 Connecting to Your ISP This file Does this Your modem is now ready to useModem software Networking If Dial-Up Adapter Do this Is listedIs not listed Go to Step If TCP/IP Dial-Up Adapter Do this Click FinishClick Add Protocol Microsoft TCP/IP OK Windows 95/98 If your ISP Do this Step Four Customizing the TCP/IP SettingsClick TCP/IP Settings Click OK, and OK Click Server assigned server address Specify an IP address, if neededClick Server assigned IP address Click Specify name server addresses and enter For you to Use this connection Check Don’t detect my modem I will select it from a list Go to Start Settings Control Panel ModemsSetting up RAS Select Remote Access Service and click Properties Click Network Click Continue to complete RAS setupSelect Start Settings Control Panel Go to Start Programs Accessories Dial Up Networking Specify an IP address by clicking TCP/IP settings Select Enable software compressionDouble-clickDial-Up Networking Make sure Use Telephony Dialing Properties is unchecked MacintoshMacintosh computers Slip or PPP dialing software System Configuration Accessing InternetInstallation Script and then configure Open Transport PPP Installing the script Transport PPP Go to Apple Menu Control Panels Modem Macintosh Go to Apple Menu Control Panels PPP Windows If You Are UsingOther Operating Systems 18CHAPTER 1 Connecting to Your ISP General rules for Using the AT Command SETUsing AT commands Overview Use the X2 result code subset Dial the following number using tone dialingTo configure your modem to Command Re-execute the last-issued command ATI5 Settings for a register in the current configurationTo display Command To change Command Getting a list Registers UnderstandingBit-mapped Registers ATO0 Command and Online ModesIf you want to Set the modem to Use this command Modes of Operation ATO1 If you want to Command Return onlineMode Return online and retrain Controlling Local Online ModeEcho Software manual Or Fax modeData and Fax Modes If the modem This indicates Returns a value Class 1 Fax Mode 6CHAPTER 3 Modes of Operation Dialing DIALING, ANSWERING, Hanging UPDial options Atdl ATD@ATD Atdr Redialing This command also defines the interval in seconds Command does. Also can be used to repeat anyDisable carrier loss redial Enable carrier loss redial Received an incoming call Manually answer a call Force Answer ModeGo through the answer sequence when it hasnt ATA International calls above 1200 bps If you want your modem CommandMaking International calls Make/Break Ratio Call DetectionPulse dialing Caller ID Functions Caller ID Modem Handles AT#CID=1 Caller ID Action CommandAn Example of Unformatted caller ID presentation AT#CID=0 Support Distinctive RingReferences Ring CommandsThere are four ring patterns in common use Are graphical depictions of each ring pattern.These Verbal Numeric Result Codes Working with Memory Memory type Applies to Loss of power will CommandNVRAM, and Flash memory ATDS2 Saving a Phone Number to Nvram AT&F1 Saving a Command String to NvramDisplaying S-Register Value Information AT&F0 AT&F2&W Substitute a template other than &F1 What format they are displayed CommandsControlling Result Code Displays Additional Result Code subsets AT&A2 Additional Result Code SubsetsAT&A0 AT&A1 Ready Controlling EIA-232 SignalingTells the modem how to respond to the DTR signal Data Terminal Data Set Ready Signal AT&C1 Business Modem sends the CD signalCarrier Detect AT&C0 4CHAPTER 7 Controlling EIA-232 Signaling Serial Port Rates Controlling Data Rates AT&B0 To allow your modem Set the serial port Command Rate asAT&B2 AT&N2 AT&N0AT&N1 AT&N9 AT&N Command ValuesSpeeds with &N and &U Speeds If &U Then your modem To limit Use this command Where x is Lowest possible connect Link Speed Index Enhance throughput Kbps46666 48000 49333 50666 52000 53333 54666 56000 57333 8CHAPTER 8 Controlling Data Rates You should be familiar with these terms before you continue Accessing and Configuring Business Modem RemotelySetting Up Remote Access Its configuration remotely AT%P0=password Accessing the Host You should see a display similar to this Configuration computer AT%B7 AT%B0AT%B6 AT%B1 You can use the AT%Fn command to control the data format Quitting a Remote-AccessPassword, return online by pressing CtrlC or typing ATO CommandsPage Dial Security Security Setting up Dial For your modem to Command Example To make the host Business Command Example ModemAT%L AT%L=PW0 Enabled Enable Local Security When using Autopass Prompting When using Password Prompting Dial Security with Password Prompting For your modem to enable CommandAutopass Dial Security Account information Example Sending AT%E=3 erases passwords for accountsMaintaining Security Accounts Dial Security by entering ATS53.0=1 For your modem to Command Enable Dial SecurityWhat the Guest User Needs to Do Dialing In From the Remote Site For your modem to be set CommandFor your modem to Command Disable Auto Answer Security Remotely 10-10CHAPTER 10 Dial Security Transmit-data flow control Flow ControlHardware and software flow control Received-data flow control Software Flow HardwareControl AT&I1 AT&R0AT&R1 AT&R2 Characters from the data stream Enable Hewlett Packard-Terminal mode. Applies only toDoes not look for your typed XON/XOFF commands AT&I4 By its attached computer Transmit-Data Flow 11-6CHAPTER 11 Flow Control Handshaking HANDSHAKING, Error Control Data COMPRESSION, Throughput Controlling the V.8 Call Indicate Tone For your modem to Command Enable the call indicate toneAttaining Speeds Above 28.8 Kbps Attaining 56 K Connections Other Protocols EnableDisable Capabilities Leveling ASL Protocols Error ControlError-Control Lower-speed AT&M4 Have no error control Normal ModeAsynchronous Mode AT&M0 Remote end until it is acknowledged by the receiving device Scheme similar to MNPFlow Control Two reasons AT&K3 For the modem to CommandAT&K0 AT&K2 Throughput results Getting MaximumThroughput Maximum Public Domain Effects Getting Maximum Throughput Page Product code, and call duration Here is a complete list of ATI n commandsDisplaying Querying and Help Screens Querying ATI11 ATI2ATI3 ATI7 AT$ For your modem to display Command 13-4CHAPTER 13 Displaying Querying and Help Screens All loopback testing conforms to ITU-T Recommendation Testing the ConnectionTesting the Business Modem using AT&Tn Testing the Business Modem using S-Register Modem using Testing the BusinessAT&Tn Using AT&T1 Using AT&T8 Loopback DL testing Request AT&T4 AT&T6, AT&T7Phone line. Data flow is shown in the figure below There are two remote digital loopback options Testing Using Keyboard Data AT&T6 14-8CHAPTER 14 Testing the Connection Remote digital loopback with built-in test pattern Testing the Business Modem using S-ResisterFor your modem to use Use one of these command Remote digital loopback using keyboard data Testing Using Keyboard Data ATS16=8 Register Starting Testing That Uses the Test PatternTo use the test pattern during Command Testing with When S16 is set to 4, the Business 14-12CHAPTER 14 Testing the Connection Problems That Occur Before Connecting Troubleshooting Business Modem wont dial For your modem to Command Enable message displayDisplay verbal messages Hear ringing but the Business Modem wont answer Double characters are appearing on your monitor Your screen displays random or garbage characters Problems that Occur After Connecting Mainframe computer keeps dropping your connection If You Still Have Problems Errors during software download Problems that Occur After Connecting 15-8CHAPTER 15 Troubleshooting Checking Your Business Modem’s Software Version Upgrading Your Modem Software to your Getting NewOperating Software Sending New Enter AT~X!. The modem should respond as follows Doesn’t Respond If Your Modem Values RegistersHow bits are Mapped to decimal 113 Converting Bits toDecimal Values 01001111 Values of the bits and entering the total Using BitsUsing Decimal Settings Bit-mapped registers have up to eight functions Complete list of S-Registers Register Default Function Bit Value Result Information about setting bit-mapped registers. For Be a problem if you expect a greatNumber of errors during a call Off their screens. When remote Enable ITU-T V.21 modulation at Up. S19=0 disables the timerTo ARQ mode only Default is 3 seconds Bit Result Default setting of zero allows no remote login Disable the remote-access busy128 Disable V.32 terbo S38 Thus enabling or disabling remote access Disable 2400 symbol rate Dial security enabledPrompting enabled Enabled 128 Disable V.FC S58 Disable precodingDisable shaping Disable V.34+ Basic Command Set Alphabetic Command SummaryCommand Function Optional parameters Command mode echo ON. Your typing will When other modems share the lineStore the number in memory using the &Z command Display help for the dial commands Errors in a non-ARQ data transfer Display the actual time. Set the clock usingControl when the speaker sounds Between command and online modes Ampersand Command Set DTR signal. Dropping DTR ends a call CD when it disconnectsMode during a call by dropping DTR With the Hn command Error control. For this to work, the remote device Software support XON/XOFF signalingRecommended setting for ARQ mode Mode only Line type Normal This setting to transfer compressed filesSelective data compression. The modem Negotiates only for V.42bis compression, Ampersand & Command Set B-9 When Carrier is lost, send a pulsed DSR signal Enable hardware flow control of received dataSend the computer a Data Set Ready DSR signal via Originate mode Send DSR after dialing, on Percent % Command Set Cancel configuration changes and restore Create and configure security accountsRemotely configure a modems serial port rate B10 115200 bps Remote configuration control Octothorpe # Command Set 14APPENDIX B Alphabetic Command Summary Hardware Flow Flow Control TemplateTemplate send AT&F1 to your modem DTE rate* Kbps None19.2 Software flow control Template send AT&F2 to the modem Basic 9600 Even 6APPENDIX C Flow Control Template Result Code Meanings Result Code Meanings SetsResult Code Meaning Wait for 2nd Dial Tone W Wait for Answer @ Result Codes Sets for Xn Values10/CONNECT Functions Schemes are supported SpecificationsTechnical Information Technical This Supports Error Control, DataDialing Adheres to the following standards Additional This feature SupportsWord Length Parity 1 Bit Stop Bits Operate asynchronously follows Pin Function Transmitted Data Received Data Signal GroundDB-25 DB-9 Mac Pin Mac Pin Description Modem Pin Modem Pin Description Most reliable performance Macintosh modem Ascii Chart 2APPENDIX F Ascii Chart FAX Information for Programmers Fax Service Class 1 CommandsFAX Service Class Following optional Class 2.0 fax commands Control Setting Fax Mode FlowFCC Notice Protocol Is making a data connection using an error controlViewing Leds This LED Status Means your Business Modem Off Has not detected the RTS signal from your computer RS232 mode has detected DTR signalUSB mode has detected successful USB registration Off RS232 mode has not detected DTR Valid range is 0*127 Registers Their Functions and Default SettingsCounts and stores the number of rings from an incoming Character. Valid range is 0*127 Disable HST Disable 250 ms pause before resultOn DTR signal, autodial the number At power-on/reset, autodial number Calls from remote users of slower Problem if you expect a greatFor HST modulation only From 1.5K bytes to 128.* for Remote digital loopback Line, and at the timeout the Business Modem hangs upS19=0 disables the timer Disable V.32 modulation used for Register Default Function Bit Value Result Thus enabling or disabling remote access. The default Disable the faster retrains that occur128 Disable V.32terbo S38 To acknowledge receipt of all transmitted data. Default = 128 Enable phase roll detection Disable V.8 Call Indicate CIReserved Enable ring type C Disable preemphasisEnable ring type a Enable ring type B Corporation Limited Warranty Warranty 3Com Client SRO# 3COM Corporation Limited Warranty J-3 FCC Certification FCC RegistrationStatement FCC Notice Radio Television Interference Canada Glossary Glossary Glossary Glossary Glossary Glossary Glossary Glossary Glossary Glossary Receiver/Transmitter Transmission rate See it rate Glossary Glossary Glossary

FLOW CONTROL

■ Hardware and software flow control

■ Received-data flow control

■ Transmit-data flow control

Overview

computer, and one for data received from the phone line.