6.0 Operation
RC224ATL/224ATLV
6.4 Data/Fax Auto Answering
EmbeddedModem Family
6.3.3 DTE Flow Control Operation
Normal operation:
Overrun Operation:
DTE does not miss character. The DTE reads the serial character sent by the
DCE. The DTE checks serial hardware overrun status and determines that an
overrun did not occur. The DTE can therefore use the character. The DTE must
send the following acknowledgment character back to the DTE.
11111110 (FEh)
DTE misses character. The DTE returns after being suspended and reads the
serial character sent by the DCE. The DTE checks serial hardware overrun status
and determines that an overrun occurred. The DTE does not use the received
character. The DTE then sends the following re-transmission request character
back to the DCE.
11110000 (F0h)
6.4 Data/Fax Auto Answering
Data/fax auto answering, when used with appropriate DTE host software, will
automatically recognize whether an incoming call is a data or fax modem. This
mechanism can be used with an integrated data/fax communication package or
with separate data/fax communication packages operating together in a
foreground/background configuration.
The auto answering mechanism is structured such that the DTE is initially
operating in the fax mode. The DTE enables auto answering using the
AT+FAA=1 command (saved in NVRAM under S27). This command should be
issued while AT+FCLASS=1. The DTE will then change its communication rate
from 19,200 bps (fax class 1 rate) to the rate expected in data mode (2400, 1200,
or 300 bps).
The DCE will attempt to establish a connection with the incoming call as a
data modem. If the incoming call is a fax, the DCE will switch to the fax mode
and establish the connection. To minimize incompatibilities with various fax and
data modems, the 59 register is used to define the length of time that the DCE has
to establish a data connection.
S9 (Range: 0–255; Default: 06) defines the time (in seconds) after going off-hook
that the DCE waits for the entire data mode handshaking process to complete
before switching to fax mode.
When a call is received (DCE sends RING result code), the DTE can initiate
the answer manually by sending an ATA command. Alternatively, the DTE can
allow the DCE to answer automatically by setting S0=non-zero value. After the
DCE goes off-hook, it will automatically determine the caller type (data or fax),
6-8
Conexant
D224ATLVDSC
CONEXANT [ CONEXANT SYSTEMS, INC ]
