COURIER HST APPENDIX E ADDITIONAL OPERATIONAL INFORMATION CONTENTS E-1 Using Both Voice and Data Communications E-2 High Speed/Low Speed Protocol E-3 Retrain Sequence E-4 PBX, Dedicated Line, and Leased Line Operations E-5 Hewlett Packard 300 Installations E-6 Analog Loopback and Other Testing E-1 COURIER HST APPENDIX E-1 USING BOTH VOICE AND DATA COMMUNICATIONS When you assemble the Courier, you have the option of plugging your phone into the second modular jack of the modem so it's available for voice calls. You can also use the phone to synchronize communications with another user whose modem uses the AT command set, such as a USRobotics or USRobotics-compatible modem. PREPARATION First call the other user to establish the bit rate, parity, word length and number of Stop bits the other person's modem accepts. Then both of you can turn the call over to your modems. COMMANDS 1. Without hanging up the phone, have your modem go off hook in Originate Mode. Type the following command: ATD NOTE: Be sure the modem is not set to X2, X4, X6, or X7, or it will return the NO DIAL TONE result code and hang up. 2. The other party should then have the remote modem go off hook in Answer Mode. The following command is used to do this: ATA 3. Now both of you can hang up your respective phones while the two modems establish the data link. They will maintain the link until one of you gives your modem a command to disconnect. Either party's device can be the originate or answer modem: it doesn't matter who made the phone call. But one modem must first enter Originate Mode and the other then enter Answer Mode. You and the other party, therefore, must agree on which command, ATD or ATA, you will each use. NOTE: It may happen that spurious garbage characters will appear on the screen when you hang up the phone. You can avoid these by hanging up the phone as soon as you hear the modem go off hook, during the one or two seconds it takes the two modems to establish the link. E-2 COURIER HST APPENDIX E-2 HIGH SPEED/LOW SPEED PROTOCOL OVERVIEW This appendix is intended for those users who want to try programming their computers to switch bit rates to match the Courier HST's connection rate. The material here applies only when the modem is set for variable rates at both the DTE (computer) and link interfaces, &B0 and &N0, respectively. In both Originate or Answer Modes, if the link rate is set to &N0 the Courier HST negotiates with the remote modem to connect at the highest possible rate. In addition, if the modem is set to the Extended or Advanced result codes (X1 or higher) it signals the DTE with one of the following result codes or, unless the call is at 300 bps, an /ARQ Mode equivalent: CONNECT (300 bps) CONNECT 1200 (1200 bps) CONNECT 2400 (2400 bps) CONNECT 9600 (9600 bps) The modem sends the result code at its previous rate. Then it switches to the new connection rate. If your computer doesn't switch rates and you want to program it to do so, use the example on the next page as a guide. It demonstrates the occurrence of the CONNECT codes in the connection sequence, so that recognition of the codes can be used to switch the computer. The example uses a sequence of incoming calls, but the codes apply to Originate Mode connections as well. The example assumes the following settings: Software: initially 9600 or 19.2k bps, allowing the full range of link rates: 9600/7200/4800/2400/1200/300 bps Modem: X1 or higher (rate-specific CONNECT codes) &B0 (variable DTE rate) &N0 (variable link rate) E-3 COURIER HST Example ----------------------------------------------------------------- Modem DTE/DCE Action Response Rate ----------------------------------------------------------------- 1. Power on. 9600 2. 300-bps call comes in. RING 9600 CONNECT 9600 3. Data link is established. 300 Data transfer takes place. 4. Data session is over. NO CARRIER 300 Call is ended; loss of carrier. 5. 2400-bps call comes in. RING 300 CONNECT 2400 300 6. Data link is established. 2400 Data transfer takes place. 7. Data session is over. NO CARRIER 2400 Call is ended; loss of carrier. 8. 9600-bps call comes in. RING 2400 CONNECT 9600 2400 9. Data link is established. 9600 Data transfer takes place. 10. Data session is over. NO CARRIER 9600 Call is ended; loss of carrier. ----------------------------------------------------------------- Explanation 1. The modem is powered on and is operating at 9600 bps. If the software is then set to 19.2k bps and an AT command sent, the DTE/DCE rate would be 19.2k bps. 2. A 300-bps modem calls. The Courier senses the incoming signal and sends the messages RING and CONNECT to the computer. These messages are sent at 9600 (or 19.2k) bps, the current rate. E-4 COURIER HST 3. Since the Courier responds CONNECT, rather than CONNECT 1200, 2400, or 9600, the computer switches to 300 bps. The modem automatically shifts to 300 bps to accept the data from the incoming call. 4. The 300-bps data session is terminated; the modem sends the message NO CARRIER at 300 bps. 5. A 2400-bps call comes in. The modem responds RING and CONNECT 2400. These message are sent at the current bit rate of 300 bps. 6. The computer, receiving the CONNECT 2400 message, adjusts accordingly to the higher bit rate. The modem also shifts to 2400 bps. 7. The 2400-bps data session is terminated; the modem sends the message NO CARRIER at 2400 bps. 8. A 9600-bps call comes in. The modem responds RING and CONNECT 9600. These message are sent at the current bit rate of 2400 bps. 9. The computer, receiving the CONNECT 9600 message, adjusts accordingly to the higher bit rate. The modem also shifts to 9600 bps. 10. The 9600-bps data session is terminated; the modem sends the message NO CARRIER at 9600 bps. NOTE: If online fallblack occurs during a 9600-bps call, the modem does not send CONNECT result codes for 7200- or 4800-bps link rates. Keep in mind that whether or not your computer adjusts to these rate changes, the Courier automatically shifts to the connection rate if it is set to &B0. E-5 COURIER HST APPENDIX E-3 RETRAIN SEQUENCE DESCRIPTION The retrain sequence occurs at 2400 and 9600 bps. It is a resynchronization sequence performed when one of the connected modems senses that problems on the line may affect data reliability. The procedure is essentially transparent to users. The following is an example of retrain events: 1. The Courier HST's receiver, sensing a need to retrain, clamps RX to MARKs. 2. The remote modem, after receiving about 100 ms of analog signals (a pattern of ?~?~ is usually output), clamps RX data to MARKs. 3. After the training sequence, approximately one second, the Courier unclamps RX data and turns HS ON. 4. The remote modem reenters Data Mode. E-6 COURIER HST APPENDIX E-4 PBX, DEDICATED LINE, AND LEASED LINE OPERATIONS The following operations apply in installations where the modem is not directly connected to the public-access switched telephone network. PBX Installations It's possible to install the modem(s) on the customer side of an analog PBX. When used with multiple telephones per line, DIP switch 7 can be set DOWN to short A/A1 when the modem is off hook. This notifies other devices sharing the line that the line is busy. Calling an Outside Party To have the modem make an outside call, follow the auto-dial instructions in Chapter 6, but insert the sequence used to obtain an outside line, followed by a comma, before the phone number in the Dial command. The off-hook indicator on the PBX should show the extension as busy if DIP switch 7 is DOWN. Internal Calling To call another modem on the PBX system, use the Dial command described in Chapter 6 with the extension of the destination modem. If set to Auto Answer, the called modem automatically answers on the incoming ring. The off-hook indicators on the PBX should show both extensions as busy if DIP switch 7 is DOWN on both modems. 2-Wire Dedicated (Private) or Leased Line A 2-Wire dedicated (private) line is a customer-installed, twisted-pair line. 2-Wire leased lines are provided by the telephone company and may be designated as 2-Wire 3002 Analog Circuits. In both types of installation there is a continuous point-to- point connection between two modems. For optimal operations, the physical length of the line should not exceed 5 miles. To establish the connection, follow these steps: 1. Decide which modem is to be the Originate modem and which the Answer modem. The originate and answer frequencies must be defined for the modems to communicate. E-7 COURIER HST 2. First put the calling modem in Originate Mode with the manual Dial command: ATD NOTE: Be sure the modem is not set to X2, X4, X6, or X7, or it will return the NO DIAL TONE result code and hang up. 3. Then put the answering modem in Answer Mode with the manual Answer command: ATA NOTE: If there is an interruption in the communications link (a strike to the line due to weather or some other problem), repeat steps 2 and 3 to reestablish the link. E-8 COURIER HST APPENDIX E-5 HEWLETT PACKARD 3000 INSTALLATIONS The Courier HST recognizes the ASCII ENQ/ACK characters exchanged between the Hewlett Packard 3000 host computer and its terminals. The HP host sends the terminal an ENQ character at predefined intervals, and sends no more data until the terminal responds with an ACK character. Courier HST modems manage this ENQ/ACK protocol so that communication is speeded up, thereby enabling HP terminals to achieve high speeds on dial-up lines. Special Received Data flow control settings (the &I command) are required for HP users. Follow these guidelines: 1. Use one of the &I settings given here for both Normal and error control (ARQ) sessions, i.e., for all &M settings. 2. Do not use a software setting for Transmit Data flow control. Set the modem only to &H0 or &H1, according to the guidelines in Chapter 4. 3. Set the Courier HST to Host Mode if it is attached to the host computer, or to Terminal Mode if it is attached to a terminal: Host Mode AT&I3 Terminal Mode AT&I4 E-9 COURIER HST APPENDIX E-6 ANALOG LOOPBACK AND OTHER TESTS ANALOG LOOPBACK SELF-TEST This test is a way to check that the modem's transmitter and receiver are working properly. During Analog Loopback, data from the computer is sent in a loop through the transmitter (where it is modulated) and the receiver (where it is demodulated), and returned to the screen. Due to asymmetrical modulation at 9600 bps, the test must be performed at 2400 bps or below. You can use the modem's internal test pattern as data, or type your own at the keyboard. Follow these procedures to test the modem by sending the test pattern: NOTE: If the modem is set to X2, X4 X6, or X7 it will return the NO DIAL TONE result code and hang up. Send the modem a different X setting. 1. Set your terminal or software to 2400 bps and send the modem the following command, which has the results listed below. AT &M0 S16=5D &M0 Sets the modem to Normal Mode. If the modem is set for error control (&M4 or &M5) you can't tell if there is a problem because the modem checks for errors and automatically retransmits any errored data. S16=5 Sets S-Register 16 to Analog Loopback with test pattern. The modem sends, modulates and demodulates its internal test pattern and returns that pattern to your screen. D The Dial command selects testing the Originate (Dial) frequency. The Answer command (A) tests the Answer frequency. The modem enters Analog Loopback Mode, goes off hook, sends the message CONNECT 2400 to the screen, and then sends the test pattern. 2. When you're satisfied with the test, terminate the operation by pressing any character key on the keyboard. The modem goes back on hook and responds with the message NO CARRIER. 3. Reset the error control default and reset S-Register 16 to zero, for data operations, by entering this command: AT &M4 S16=0 E-10 COURIER HST Normal/Test Frequencies In normal operations, communicating modems transmit at different frequencies within the communications channel, one low and the other high. The calling modem is said to be in Originate Mode: it transmits at the low (Originate) frequency and receives at the high frequency. The answering modem, in Answer Mode, transmits at the high (Answer) frequency, and receives on the low frequency. During Analog Loopback testing, the modem transmits and receives on the same frequency, either Originate (low) or Answer (high). The Analog Loopback command in the previous section tests the Originate frequency. Testing the Answer Frequency To test the Answer frequency, substitute the Answer command, A, as follows: AT &M0 S16=5A ADDITIONAL TESTS In all, S-register 16 has five settings, as follows. 0 Data Mode (normal operations) 1 Analog Loopback 2 Dial Test 4 Test Pattern 5 Analog Loopback with Test Pattern NOTE: After any testing, be sure to reset S-register 16 for Data Mode, with or without the default error control setting (&M4): AT &M4 S16=0 S16=1 1. Select this option to perform analog loopback testing by sending your own data instead of the test pattern. Use either of the following commands after setting your terminal or software to 2400 bps. If the modem is set for error control, insert &M0 before the S16 command. ATS16=1D ATS16=1A 2. When the modem displays the message CONNECT 2400, type any message you wish at the keyboard. It is looped through the modem and returned to the screen. E-11 COURIER HST 3. End the test by not typing anything for at least one second and then typing the escape code that brings the modem back to Command Mode. (Do not type the AT prefix or press the Enter key.) +++ 4. The modem returns the OK message. Reset the error control default and reset S-Register 16 to zero, for data operations, by entering this command: AT &M4 S16=0 S16=2 The Dial Test is used for factory testing the frequencies of Touch-Tone values. When S-register 16 is set to 2 and a single Touch-Tone is dialed (e.g., ATD7), the modem continues to transmit that tone until another Carriage Return is entered. S16=4 The Test Pattern alone is used for testing equipment and the phone line. If S16 is set to 4 and a Dial command issued, the Courier transmits the test pattern upon connection to the remote system. If set for Auto Answer the Courier transmits the test pattern when it answers a call. Be sure to reset S16 to zero for normal calls. Testing at 1200 BPS To test the modem at 1200 bps, follow the previous instructions, but first set your software to 1200 bps. Testing at 300 BPS The Test Pattern is not available at 300 bps. Analog Loopback testing is done at 300 bps by setting your software to 300 bps and setting S-16 only to 1D or 1A. NOTE: It might happen that you have issued either S16=1 or 5 and the modem is in Analog Loopback Mode, but you haven't yet sent a Dial or Answer command to initiate testing. If the modem is also set for Auto Answer and a call comes in, the Courier resets S16 to zero and answers the call. E-12