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Modem 34336
2.4.8 V.29 F
AST
M
ASTER AND
S
LAVE
M
ODES
(Q
UICK
S
ETUPS
14
AND
15)
In multidrop operation, the master modem transmits to all of the slave
(remote) modems. When the DTE at a slave site recognizes its own address in
the polling protocol, it raises RTS to the slave transmitter. The slave responds
by transmitting a special training sequence, then raising CTS and transmitting
the data from the DTE. When the DTE has completed transmission, it lowers
RTS and the modem will drop carrier to let the next modem on the poll list
use the channel.
The V.29 Fast Master and Fast Slave modes support data rates of 4800, 7200,
and 9600 bps. The leased lines can be conditioned or unconditioned. The
master modem must be set to originate mode, and the slave modem must be
set to answer the mode. (The Answer/Originate option is automatically set to
these settings when the V.29 Fast Master and Fast Slave Quick Setups are
used.)
Slave-to-Master (Inbound) Transmission
When the remote modems come on-line, they automatically synchronize to
the incoming carrier and train on the data stream from the master modem.
Slave-to-master transmission is always switched carrier operation under
control of the RTS signal from the DTE. An anti-streaming timer built into
the modem will (if enabled) halt transmission if the DTE holds RTS on for
more than 30 seconds. The assumption is that if RTS is held on for more
than 30 seconds, there is a fault in the DTE.
If you access the TIA/EIA status screen on the LCD display when a slave
modem is transmitting to the master modem, the status screen will typically
look like this:
TR MR RS CS TD
9600 CD RD
Typically TD, CD, and RD will flash on the master modem, and RS, CS, TD,
and RD will flash on the slave modems.