&T6 - Initiate Remote Digital Loopback
Command Line Format
AT [cmds] &T6 ;
Suffix Values
N/A
Default
N/A
Stored by &Wn
N/A
Displayed by &V
N/A
Description
The command is only valid if the modem is in the Online Command State,
the modulation is one of the Quadrature Amplitude Modulation (QAM) types
that support full-duplex transmission, and the speed is the same in both
directions. The command is not valid for any Frequency Shift Keying (FSK)
modulation (e.g., V.21 and V.23).
Recommendations V.22 and V.22bis specify control of remote digital loopback
for V.22 and V.22bis modems. Recommendation V.54 specifies control of loopback
on other types of full-duplex modems.
The modem sends the remote digital loopback request signal to the distant
modem. After the RDL acknowledgment signal is received from the distant
modem, the following occurs:
DSR is turned off (if &S1 is in effect)
Online State is entered,
CONNECT result code is sent to the DTE,
Test timer is set to the value in S18.
If the modem does not receive the RDL acknowledgment signal from the distant
end in 3 seconds, it sends an ERROR result code to the DTE and returns to
the Online Command State.
The modem sends the signal to release the remote digital loopback when the
test is terminated. The test may be terminated by the H0, Zn, or &T0 command.
The test also terminates when the test timer expires (sending the modem
to the Online Command State) or carrier is lost (causing a NO CARRIER result
code and the modem to go on hook in the Idle State).
Result Codes
CONNECT - when Online State is entered.
ERROR - if any V.54 test is active (&T1, &T3, &T6-&T8).
ERROR - if not in Online Command State.
ERROR - if command is invalid.
ERROR - if the RDL signal is not acknowledged.
Execution Time
Command execution lasts for the time it takes to receive the RDL acknowledgment
signal plus the test time.
DTE Interface Lines Affected
DSR
LEDs Affected
MR flashes
Cross Reference
Commands - &Sn, &T0,
&T7, Hn - Control
The Switchhook , Zn - Perform Soft Reset
S-registers - S18
DTE signals - DSR
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