Intel 536EX 3.9Diagnostic Testing S18, &Tn, 3.9.1Local Analog Loopback AT&T1, Intel Confidential

Data Mode AT COMMANDS

Table 17. Resulting Modem-to-Modem Connection Rates with Non-Default Values

Originating Modem	Answering Modem	Resulting Connection Speed
+MS = V34, 1, 0, 0, 0,	+MS = V32, 1, 0, 9600,	9600 bps: the originating modem is configured to attempt
0;	0, 0;	a maximum 28,800 bps connection, but the answering
the UART data rate =	the UART data rate =	modem is configured to attempt a maximum data rate of
115,200 bps	14,400 bps	9600 bps.
+MS = V34, 0, 33,600,	+MS = V32B, 1, 0,	No connection: the originating modem is configured to
33,600, 0, 0;	9600, 0, 0;	attempt only a 33,600 bps connection, but the answering
UART data rate =	B1 and UART data rate	modem is configured to attempt a maximum data rate of
115,200 bps	= 14,400 bps	9600 bps.
+MS = V32,		9600 bps: the originating modem is configured to attempt
	+MS = V34, 1, 0,0, 0, 0;	connection at between 7200 to 9600 bps or below. The
1, 7200, 9600, 0, 0;
	UART data rate =	answering modem is configured to attempt a data rate of
and UART data rate =
	9600 bps	9600 bps or below. The connection takes place at
7200 bps
		7200 bps, the highest speed supported by both modems.

3.9Diagnostic Testing [S18, &Tn]

The &Tn command initiates loopback tests. Setting S-register S18 to a non-zero value determines the length of testing after the modem receives the &Tn command. After the testing period elapses, the modem halts the test and returns to command mode. To abort the test before the test timer has timed out, enter the escape code sequence followed by AT&T0. Setting S18 to an ’0’disables the test timer. In this case, the loopback test continues to run until an escape code, followed by AT&T0 (or ATH), is sent to the modem.

The modem provides a local analog loopback test (see Section 3.9.1, “Local Analog Loopback [AT&T1]” on page 36) for testing modem-to-modem integrity in all modes except V.90 and V.92. After entering the loopback mode, the communication integrity is checked by the DTE sending data to the modem and then checking the looped-back data for errors. In addition, in the self-test mode the modem implements an internal data pattern generator and checker that detects errors. When a data error occurs in self-test mode, the modem increments an internal error counter. Upon completing the test, the modem sends a three-digit error count to the DTE. These tests are illustrated in the following examples.

3.9.1Local Analog Loopback [AT&T1]

This test is used by the local DTE to check the DTE-to-modem communication integrity. The local DTE will not initiate the test from online command mode.

36 536EX Chipset Developer’s Manual

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