SPORTSTER 14,400 APPENDIX F. MODEM TESTING Modem testing is available with the &T command and Register S16 (Dial test). All loopback testing conforms to CCITT Recommendation V.54. NOTE: Only one test can be performed at a given time. If you send a test command while the modem is in test mode, you'll receive an ERROR message. TESTING WITH &T The tests supported through the &T command include analog loopback, digital loopback and remote digital loopback. You can key in your own data during testing, or use the modem's internal test pattern and error detector. In all cases, disable error control before testing. If the modem is detecting errors and retransmitting the affected data, your test results will be invalid. Ending a Test_&T0, S18 Issuing the &T0 command terminates a test. Alternatively, set Register S18 to a specified number of seconds, for example, S18=10. When the 10 seconds are up, the modem automatically ends the test and returns to Command mode. If the test was Analog Loopback, the &T0 command hangs the modem up. If the test was Digital or Remote Digital Loopback, issue an ATH command to hang up the modem, or an ATZ command to hang up the modem and reset it to its defaults. NOTE: If you use the S18 test timer, but in the process of testing you issue an ATZ command, S18 resets to zero and the timer is disabled. Also, you cannot store a value for S18 in nonvolatile mem ory: its power-on and reset default is always zero. Analog Loopback_&T1, &T8 This test checks the operation of the modem's transmitter and receiver. Data flow is shown in Figure F.1. Modem/DTE indicates the modem's interface with the computer (Data Terminal Equipment). Figure F.1_Data Flow During Analog Loopback There are two analog loopback options. The first, &T1, involves your typing data that you can verify at your screen. The second option, &T8, is an internal self-test that does not involve the keyboard or screen. It isolates the modem from the computer interface to give you a more specific result. &T1 1.The modem should be on hook in Command mode. If you wish, set Register S18 as a test timer. For example, insert S18=10 in the following command string before &T1. AT &M0 S18=1 &T1 The modem disables error control, sets the timer, enters analog loopback (AL) mode, and sends a CONNECT message. 2.Type recognizable data so that you can verify it when it is looped back to the screen. 3.End the test. If you set S18, the modem automatically stops the test at the timeout, exits AL mode and responds OK. If you didn't set Register S18, wait one second and type +++ to end the test and return the modem to Command mode. When the modem responds OK, type AT&T0 to terminate AL mode and hang up the modem. (Typing ATH has the same effect. Typing ATZ also has the same effect, but also resets the modem and restores your &M default.) The modem responds OK. If the modem sends an ERROR message, you have issued an invalid command. 4.If there were no errors, reset the modem to &M4, for error control, unless you've issued the ATZ reset command. NOTE: If the modem is in Online- Command mode, that is, still connected to a remote modem, and you send it an &T1 or &T8 command, it drops the call, enters AL mode, sends a CONNECT result and waits for loopback characters. &T8 This AL option causes the modem to send an internal test pattern to its transmitter and loop it back to the receiver. An internal error detector counts any errors and, when the test is ended, sends the number of errors or 000 (no errors) to the screen. Since you don't type anything during this test, and the modem does not send anything to the screen, this option veri fies only the modem. If there are no errors but your problem continues, it may be at the computer interface. 1.The modem should be on hook in Command mode. If you wish, set Register S18 as a test timer. For example, insert S18=10 in the following command string before &T8. AT &M0 S18=10 &T8 The modem disables error control, sets the timer and enters AL mode. The modem sends its internal test pat tern to the transmitter, and loops the pattern back to the receiver. You will not see any data on your screen. 2.End the test. If you set S18, the modem automatically stops the test at the timeout. If you didn't set Register S18, type AT&T0 to end the test. Or use ATH or the command that resets the modem, ATZ. Both of the latter end the test and hang up the modem. When the modem hangs up it returns a three-digit code, followed by OK. A code of 000 indicates no errors were found. A code of 255 indicates 255 or more errors. An ERROR message indicates that you issued an invalid command. 3.If there were no errors, reset the modem to &M4 for error control unless you issued the ATZ command. &T2 This option is reserved. Digital Loopback_&T3 If your modem has passed the AL test, this test can help you locate a problem with a remote modem or the telephone channel. Figure F.2 shows the data flow during Digital Loopback (DL) testing. Modem/DTE indicates the modem's interface with the computer (Data Terminal Equipment). Figure F.2_Data Flow During Digital Loopback 1.Set the modem to &M0, to disable error control. Establish a connection with the remote modem. 2.Bring the modem back to Online- Command mode with the +++ escape code. Then send it the AT&T3 command. The modem enters DL mode. 3.The remote user should type a short message. It will be looped back by your modem's transmitter for verification on the remote screen. You will not see the message or any other data. 4.When the remote user has completed the test, issue the AT&T0 command to end the test. If you wish, return the modem online (ATO) to resume data mode. Or type either ATH or the command that resets the modem, ATZ. The latter two commands end the test and hang up the modem. The modem responds OK. If the modem sends an ERROR message, you have issued an invalid command. &T4, &T5 The &T4 option causes the modem to grant a remote modem's request for a Remote Digital Loopback test. The &T5 option cancels &T4, and the modem fails to recognize such a request. This is the default so that your modem isn't subject to another user calling and tying up your modem without your permission. Remote Digital Loopback_&T6, &T7 This test, like the local digital loopback test, verifies the condition of both modems and the phone link. Data flow is shown in Figure F.3. Modem/DTE indicates the modem's interface with the computer (Data Terminal Equipment). Figure F.3_Data Flow During Remote Digital Loopback The request for and granting of Remote Digital Loopback testing requires that both modems use CCITT V.54 standard signaling. The test must be performed at 2400 or 1200 bps. If the remote mo dem does not have the capability or is not set to respond, you will get an ERROR result code. As with Analog Loopback, there are two Remote Digital Loopback options. If you select &T6, you send keyboard data to the modem and verify it when it is returned over the phone lines and to your screen. If you select &T7, the modem sends its internal test pattern and returns an error count to your screen. &T6 1.Set your software to 2400 or 1200 bps. Set the modem to &M0. If you wish, set the S18 timer. Establish a connection with the remote modem. If you haven't already done so, arrange with the remote user to cooperate with your testing. The remote user should set his or her modem to acknowledge the RDL request, for example, AT&T4. 2.Bring the modem back to Online- Command mode with the +++ escape code. Send it the AT&T6 command. The modem enters RDL mode. 3.Type a short message. It will be looped back to your modem by the remote modem and to your screen for verification. (The remote user will not see your data.) 4.End the test. If you set Register S18 the modem automatically ends the test when the test timeout is reached. If you didn't set S18, type AT&T0 to end the test. If you wish, return the modem online (ATO) to resume data mode. Or send either ATH or the command that resets the modem, ATZ. The latter two commands end the test and hang up the modem. The modem responds OK. If you issue an invalid command, the modem sends an ERROR message. Data errors indicate a problem with the remote modem or the phone link. If you have not performed analog loop back testing with your modem, the problem may also lie with your modem. 5.Reset the modem to &M4 unless you used the reset command, ATZ. &T7 This test option causes the modem to send an internal test pattern through the Remote Digital Loopback. An internal error detector counts any errors and, when the test is ended, sends the number of errors or 000 (no errors) to the screen. You don't need to type anything during this test. The modem sends only its final error count to your screen. 1.Set your software to 2400 or 1200 bps. Set the modem to &M0. If you wish, set the S18 timer. Establish a connection with the remote modem. If you haven't already done so, arrange with the remote user to cooperate with your testing. The remote user should set his or her modem to acknowledge the RDL request, for example, AT&T4. 2.Bring the modem back to Online- Command mode with the +++ escape code. Then send it the AT&T7 command. The modem enters RDL mode. The modem sends its internal test pattern to the remote modem, which loops it back to your modem. You will not see the data on your screen. 3.End the test. If you set S18, the modem automatically stops the test when the timer times out. If you didn't set Register S18, type AT&T0 to end the test. After you view the test results (next paragraph), return the modem online if you wish (ATO) and resume data mode. Or send either ATH or the command that resets the modem, ATZ. The latter two commands end the test and hang up the modem. When you terminate the test, the modem returns a three-digit code, followed by OK. A code of 000 indicates no errors were found. A code of 255 indicates 255 or more errors. If you issue an invalid command, the modem sends an ERROR message. If you've performed an Analog Loopback and know your modem is working properly, errors indicate a problem with either the phone connection or the remote modem. 4.Reset the modem to &M4 unless you've sent it the ATZ reset command. DIAL TEST_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 (for example, ATD7 ), the modem con tinues to transmit that tone until you press the Enter key again.