SPORTSTER 14,400 CHAPTER 3. QUICK START This chapter provides an overview of basic modem settings and is designed to quickly get you started using your Sportster 14,400. ù If you're already familiar with dial-up modems, you may want to skip ahead to the Recommended Settings section later in this chapter. There you'll find sugges tions to help you make the best use of the Sportster 14,400. ù If you're a new modem user, the next few sections provide some general useful information on modems. Both new and experienced users may want to refer to Chapters 4 through 7, as well as the Glossary and Index, for detailed information on each modem feature as well as the terms and concepts discussed here. BASIC OPERATING REQUIREMENTS For successful data communications to occur, your communications software and modem require that you set some minimal parameters. Software Parameters Your communications program requires the following parameters. ù The computer or terminal serial port to which you've attached the modem ù The data rate between the computer and modem_also referred to as serial port rate_in bits per second ù Parity_usually None or Even ù The number of Stop bits_the final bit(s) attached to a data character before transmission ù Word length_the number of bits in a data character without parity, Start and Stop bits When the modem receives an AT command issued from the keyboard or software, it detects the serial port rate and data format and uses them as its operating parameters. The remote system must use the same word length, parity and number of Stop bits. If you don't know what the remote system re quires, phone to find out before trying to connect via modem. Modem Parameters The modem is shipped ready to dial out and connect with other modems except for Transmit Data flow control. Don't try to make a high-speed call without first setting the modem for this function. See the Recommended Settings and Alternative Settings sections later in this chapter. Setting Modem Parameters To change the modem's settings, load your communications software and follow the procedures your software specifies to reconfigure the modem. Various programs may require that you do one of the following. ù Insert modem settings in each Dial command string in the program's Dialing or Phone Directory. ù Create a modem setup string of commands. ù Send commands directly to the modem (if your program displays a cursor on a Terminal screen). The following is an example of modem parameter settings. AT &H1 &B1 The &H1 command tells the modem to use hardware flow control, and &B1 fixes the serial port rate at the rate of the last AT command. RATE SHIFTING The modem has two interfaces at which it transmits and receives data: the serial port interface, which it shares with the computer or terminal, and the phone line interface. Phone Line Interface The Sportster 14,400 and compatible remote modems go through a connection sequence to try to connect at the highest possible rate. As long as your software is set to at least 19.2K bps and the modem has detected that rate through an AT command, the modem is always able to connect at 14.4K bps. If the remote modem is operating at a lower rate, your modem drops its rate to connect and the call proceeds at the lower rate, for example, 2400 bps. This is called the connection rate. Serial Port Interface As mentioned earlier, the modem detects its operating rate from its last received AT command. After that, the modem determines its serial port rate in one of the following ways. Note that in both cases, your software must also be set to support the same serial port rate option. 1.If the modem and software are set for variable serial port rates, both the modem and the software shift their port rates to match any rate switching at the phone line interface. If the modem connects with a remote modem at 2400 bps, for example, you will find after your call that your software setting has switched down to 2400. If you want to dial out at 9600 bps, change the software setting first, before instructing the modem to dial. 2.If the modem and software are set for a fixed serial port rate, the rate at the serial port does not drop down to match a lower connection rate. This allows you to lock in a higher rate at the port (for example, 38.4K or 19.2K bps) for very efficient transmission between the modem and the terminal. You'll find instructions in the following section, Recommended Settings. If your software supports a fixed serial port rate, you will achieve greater throughput with this option. Particularly if the modems connect under data compression, a fixed, high serial port rate can more than triple the amount of data that goes from one computer to the other each second, and keep your phone line costs to a minimum. RECOMMENDED SETTINGS We recommend using all of the modem's factory settings except for flow control and the serial port rate. Flow control is factory-set as disabled; we recommend that you enable hardware flow control. The serial port rate is factory-set as variable; we recommend that you set a fixed, high serial port rate (as described above). Note that to use these recommended settings, your machine and software must also support them. Check the quick configuration guide that came with the modem to see if your communications program is listed and what it supports. If your program is not listed, review your software documentation. If the software doesn't support either hardware flow control or a fixed rate at the computer interface, review Alternative Settings, after this section. Check your software or terminal documentation to see if your machine supports the recommended settings. Apple computers, for example, do not support a fixed serial port rate or hardware flow control (Clear to Send/Request to Send signaling). Software Settings Hardware flow control: Select your software's option for hardware flow control. Many programs combined CTS/RTS as one option. NOTE: All 100% IBM-compatible computers support hardware flow control. Some software supports both hardware and software flow control, but requires you to turn off the kind you're not using. Check your software manual. 38.4K or 19.2K bps: Set a high data rate between the modem and the computer. A rate of 19.2K bps is required to make a 14.4K bps connection, however 38.4K bps provides the greatest efficiency when a call is under error control and data compression. NOTE: If you are certain that your software, computer, and serial card (if you have one) can handle 57.6K bps, you can use this higher speed. We recommend that you use this speed only if necessary; you could lose data if part of your system can't handle 57.6K bps. If you're not sure of your system's capabilities, use 38.4K bps, which is efficient and reliable. Fixed Rate: Many programs that support a fixed serial port rate control this function with an Auto Baud Detect toggle. Toggle Auto Baud Detect OFF and the software data rate will remain high, even if the phone connection is as low as 300 bps. If your software calls this Locking the Port Speed, select this option. Modem Settings &H1 Clear to Send Hardware flow control: the modem sends CTS signals to the computer or terminal to control the data flow. Flow control is required for error control and when the serial port rate is higher than the connection rate. (The &H2 setting, software flow control, may affect data reliability. See Example 2 in the next section, Alternative Settings.) &R2 Request to Send hardware flow control: the computer or terminal sends RTS signals to the modem to control the data flow. &B1 The modem's serial port rate is fixed at the rate of the last AT command. It does not switch to match the phone connection rate when the modem connects with a remote modem at a lower rate. Your software must first be set to a fixed rate, as shown under the previous heading, Software Settings. If your software supports the &H1, &R2 and &B1 options, we recommend that you make them your power-on and reset defaults by writing them to nonvolatile memory. See Page 3-9. NOTE: The next section, Alternative Settings, shows how to set the modem if your software does not support the above options. Also included are recommended settings if you will normally use software flow control but plan to use an Xmodem-type protocol, and guidelines on transferring files that are already compressed. ALTERNATIVE SETTINGS 1.Your software doesn't support Clear to Send, but supports XON/XOFF signaling. &H2 Software flow control: the modem sends Ctrl-S and Ctrl-Q (XOFF/XON) characters to the computer or terminal to control the flow of data. &B1 As above, under Recommended Settings, providing your software supports a fixed serial port rate. WARNING: Software flow control is not recommended because Ctrl-S or Ctrl-Q characters that occur in a file, or in a file transfer protocol such as Zmodem, may be misinter-preted and dropped from the data stream by the modem or receiving computer. Set the modem to &H2 or &H3 only if you are transferring text files. 2.Your machine or software doesn't support Clear to Send, and you're using an Xmodem-type file-transfer protocol. &H0 Factory setting. Flow control disabled. Do not use software flow control (&H2), because the protocol uses the Ctrl-S and Ctrl-Q characters that will be misinterpreted as flow control characters, and you risk losing data. &B0 Factory setting. The serial port rate switches to match the connection rate of each call. Recommended because there is no flow control. Be sure also to set your communications software to switch its rate. Turn ON the Auto Baud Detect option, unlock the serial port, or select whatever setting the program requires. &M0 Error control disabled; recommended because there is no flow control. CAUTION: Many Xmodem-type protocols are available. However, keep the following limitations in mind. ù Most of these protocols perform error control, which makes them safe for calls at all rates from 14.4K down to 300 bps. Ymodem-G, however, should not be used with the above modem settings, because its response to errors is to abort the call. Earlier versions of Zmodem did not perform error control and should also be avoided. Current versions of Zmodem, however, are highly recommended. See Throughput Guidelines in Chapter 4 or appendix A for more guidelines. ù Because flow control is disabled, the data packets transferred by the protocol should be less than 1,000 bytes in size, and should not be of the sliding-window type. Review the protocol documentation before using the protocol. If the packets are too large, and there is no flow control, you risk losing data. 3.Your system doesn't support either Clear to Send or XON/XOFF signaling. &H0 Factory setting. Flow control disabled. &B0 Factory setting. The serial port rate switches to match the connection rate of each call. Required because there is no flow control. &M0 Error control disabled, required because there is no flow control. CAUTION: We recommend that the modem settings just described never be used for calls above 2400 bps unless you're using an error-control file- transfer protocol. See the cautionary notes under Example 2. 4.Your software does not support a fixed rate at the serial port interface. &B0 Factory setting, variable serial port rate: this rate switches to match the connection rate of each call. This does not affect error control or flow control. NOTE: You will not gain the throughput efficiency that occurs when the serial port rate is fixed at a higher rate than the connection rate. In addition, at the factory setting for data compression, &K1, the modem disables compression when the connection rate is set to &B0. When the serial port and connection rates are equal, data compression gives no advantage. In fact, data compression operations add time to the call. 5.You are calling a non-MNP modem. S27=16Disable MNP handshaking. A non- MNP modem may misinterpret the MNP link request and prevent a successful connection. If the remote modem uses V.42 error control, the modems will connect under V.42 error control. Otherwise, they connect without any error con trol. Note that this applies only if you are calling a non- MNP modem. 6.You are transferring already compressed files. &K3 This disables MNP compression, which does not work successfully with files that are already compressed. If the remote modem is able to use V.42 bis compression, you will gain optimal throughput. DATA FORMAT Your communications software and the remote communications software must be set to the same word length, parity, and number of Stop bits. Information Services and Bulletin Boards make this information readily available. If you don't know what the remote system requires, phone first to find out. If you have trouble connecting with a remote system, the reason may be the wrong word length/parity/Stop bit combination. The Sportster modem is set at the factory to a 7-bit word length, even parity, and 1 Stop bit. Some communications programs use a shorthand method to refer to this format: 7-E-1. If you wish to call a remote system that requires a different format, set your software to the correct parameters before you attempt to dial out. When the modem receives the dial command, it detects the new data format from the AT command prefix. One Start bit is universal and not programmable. The other allowable options are listed in the following table; with the Start bit they form a ten-bit data unit. Table 3.1_Allowable Data Formats Word Parity Stop Length (1 Bit) Bits 7 Even, Odd, 1 Mark, Space 7 None 2 8 None 1 STORING DEFAULTS IN NONVOLATILE MEMORY Write your default configuration to nonvolatile memory (NVRAM) with the &W command. First, set your software to the desired communications parameters, for example: Serial port rate 38.4K bps Word length 8 Parity None Stop bits 1 The following command example sets the modem for the current session, and stores the settings inserted before &W as defaults. These include the above parameters that the modem detects from the rate and format of the AT command prefix. AT &B1 &H1 &W As long as DIP switch 7 is UP (OFF), the modem loads the defaults from NVRAM at power-on and reset, including the rate and format defaults. Be sure to type &W last in the string, before pressing the Enter key. DIALING Use the following command format, beginning with the AT prefix and issued by pressing . The maximum number of characters in a command string is 40. The modem defaults to pulse dialing: the T in the command enforces tone dialing. ATDT phonenumber To redial the number, you can use the repeat command. A/ This command causes the modem to re- execute the command in the command buffer. If you've sent an additional command to the modem, that command now occupies the buffer.