Z02215
Single Chip Modem with Integrated Controller, Data Pump, and AFE
18
Table 3. AT Command Set (Continued)
Function and Description
Command
B4
The Minitel compatibility mode is activated by this
command. It defaults to master mode (Tx75/Rx1200) if the
modem is the originator.
If S-register S37 is 1, Minitel line reversals are supported.
Minitel allows a modem using V.23 and transmitting at 75
bps to simultaneously switch its transmitter to 1200 bps and
receiver to 75 bps. The other V.23 Minitel modem detects
the rate change and switches its transmitter to 75 bps and
receiver to 1200 bps. The \R and R commands describe
methods of causing a Minitel line reversal during a V.23
connection.
When S-register S37 is set to any value other than 1, then a
setting of B4 operates as if B0 was set.
B5
When S-register S37 is 1 (V.23) or 2 (Bell 202T), the
modem assumes that a 4-wire telephone connection exists.
Both the transmitter and receiver use the 1200 bps
telephone line data rate. This mode does not operate
properly unless a 4-wire telephone connection exists.
When S-register S37 is set to any value other than 1 or 2,
the B5 option operates as if B0 is set.
&C
Data Carrier This command determines how the modem’s DCD signal relates to the carrier
Detect
Options
signal (RLSD) from the other modem. This option takes effect only at the
beginning of a telephone line connection. If &C is issued from the COMMAND
state, no immediate effect results.
&C0
During asynchronous operation (&Q0 in effect), DCD is on
at all times. During synchronous operation (&Q1, &Q2 or
&Q3), DCD reflects the state of the carrier signal from the
other modem using S-registers S9 and S10. This command
is the default value in North America.
&C1
This command reflects the state of the carrier signal from
the other modem using S-registers S9 and S10.
PS001907-0904
AT Command Set
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