3Com 56K manual 14-8CHAPTER 14 Testing the Connection

14-8CHAPTER 14: TESTING THE CONNECTION

Testing Using a This test option causes the modem to perform a remote digital loopback Built-in Test Pattern test by sending a built-in test pattern. An internal error detector counts

(AT&T7) any errors and, when the test is ended, sends the number of errors or 000 (no errors) to the screen.

Follow the steps below. However, you don't need to type anything during this test. The modem sends only its final error count to your screen.

1Send AT&M0&N3S14.0=0 to prepare the Business Modem for testing.

This command disables error control, fixes the connection rate at 2400 bps, and makes the Business Modem return to command mode when you type the escape code (+++).

2Establish a connection with the remote device.

3If you haven't already done so, arrange with the remote user to cooperate with the test.

If necessary, set the remote device to acknowledge the remote digital loopback request. For example, older 3Com modems need to be set to S16=8.

4Send AT&T7 to the modem. The modem enters remote digital loopback mode, and the MR status light flashes.

The Business Modem sends its built-in test pattern to the remote device, which loops it back to your Business Modem. You will not see the data on your screen.

5Send the escape code, +++, and then AT&T0 to end the test. You can also end the test by sending ATH, ATZ, or ATZ! Be careful, though, because ATZ and ATZ! reset the Business Modem in addition to ending the test.

If you issue an invalid command, the Business Modem sends an ERROR message. If you set Register S18, the Business Modem automatically ends the test when the test timeout is reached. See the example in the previous section, Stopping a Test for an example of using S18.

When the test ends, the Business 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.

Data errors indicate a problem with the remote device or with the phone link.

6Send AT&M4, unless you used a reset command (ATZ or ATZ!).