Z02215 Datasheet, PDF (37/74 Pages) Zilog, Inc. – Single Chip Modem with Integrated Controller, Data Pump, and Analog Front End

Z02215
Single Chip Modem with Integrated Controller, Data Pump, and AFE
31
Table 3. AT Command Set (Continued)
Command
R
Line
Reversal
Command
and Option
Function and Description
When issued to the modem transmitting at 75 bps during Minitel V.23 operation
(B4 and S register S37 is 1), this command causes the transmit data rate to
change to 1200 bps and the receive data rate to change to 75 bps. If the remote
modem supports and is configured for Minitel operation with line reversals, it
automatically detects the rate switch and changes its own transmit and receive
data rates.
When issued to modems in the IDLE state (no connection), this command
causes the modem to attempt to establish its next connection using the reverse
data band, as described below.
The V.22bis, V.22, Bell 212, V.23, Bell 202, V.21 and Bell 103 data modes each
support two data bands. One data band is used to transmit data, the other to
receive. The modem picks which data bands it uses for transmit and receive
according to whether it is the calling or answering modem for the connection. If
the data bands are reversed, the modem will not be able to establish a
connection with another modem unless that modem's data bands are also
reversed.
By issuing this command to both the calling and answering modems, a V.23
Minitel connection (command B4) may be started with the calling modem
transmitting at 1200 bps and receiving at 75 bps.
This command may be used before establishing a connection in any data band,
and affects only the next connection.
If the modem is in the IDLE state, the R command configures the modem to
enter STATIC REVERSE mode when a Minitel connection is made. If the
modem has a connection and is in Minitel MASTER mode then issuing the R
command performs a direct turnaround. If the reversal is successful then the
modem returns OK. If the reversal is unsuccessful, the modem returns OK.
Otherwise, it returns NO CARRIER. If the modem is not in MASTER mode,
ERROR is returned.
When B4 and S-register S37 are 1 and the terminal is transmitting at 75 bps
during Minitel V.23 operation, the transmit and receive rates change to 1200
bps and 75 bps respectively. If the remote modem supports and is configured
for Minitel operation with line reversals, it automatically detects the rate switch
and changes its own transmit and receive data rates. See “Minitel Line
Reversal” on page 44 for details.
Note: R may be followed the O command in the command line to return ON-
LINE immediately.
PS001907-0904
AT Command Set