Product data

USRobotics
Command Reference
Fax Class 1 and Fax Class 1.0 Commands - 111
returns to command mode.
The modem concludes an error is detected if carrier is lost for any period of time
during or before the reception of a frame. If carrier is lost for a time period longer
than the time specified by the register S10, the modem finishes delivering the data
in the receive buffer (if any) to the DTE, sends <DLE><ETX>, generates the
ERROR message, and returns to command mode. All subsequent data received
from the remote is discarded.
If the modem detects a frame abort sequence (seven consecutive ones with no
zero insertion) while it is waiting for a frame beginning flag (it was receiving HDLC
flags), it will wait for the HDLC flags again until either carrier is lost, or the DTE
aborts the process by sending an abort character or by dropping DTR with &D2 in
effect. If the frame abort sequence is detected while the modem is receiving a
frame it finishes delivering the data in the receive buffer (if any) to the DTE, sends
<DLE><ETX>, generates the ERROR message, and returns to command mode.
The modem keeps looking for HDLC flags followed by more data from the remote,
with the selected modulation scheme.
If the modem detects a receive buffer overflow condition, it concludes that there
was an FCS error in that frame. The modem will receive more frames only if a
starting flag is detected and there is room in the receive buffer. If a starting flag is
detected and there is no room in the buffer, the modem discards all data in that
frame.
If the modem receives any character from the DTE after the +FRH command
(except flow control characters if software flow control is in effect), or if the modem
detects a high-to-low transition of the DTR signal while &D1 is in effect, it sends
<DLE><ETX> to the DTE, generates OK result code, and returns to command
mode. The receive buffer is cleared and all data received from the remote is
discarded. If the modem detects a DTR drop while &D2 is in effect, it goes on-
hook, sends <DLE><ETX> to the DTE, generates OK result code, and returns to
command mode. If the modem detects a DTR drop while &D3 is in effect, the
modem performs a warm reset.
Fax Data Transmission
Fax data transmission is initiated by the AT+FTM=<mod> command. After this
command is issued, the modem generates the CONNECT message and
transmits carrier in the modulation scheme specified by the parameter n. The
modem then transmits constant 1 bits for a minimum of one second and continues
to transmit constant 1 bits until it receives a character from the DTE.
When data is received from the DTE, the modem deletes start and stop bits and
deletes all <DLE><chr> character pairs before transmitting the data to the remote.
Each <DLE><DLE> sequence is transmitted as a single <DLE>. <DLE><ETX> is
considered as the end of stream marker, and is not transmitted. All data received
from the DTE after the <DLE><ETX> is ignored by the modem until the modem
generates either the CONNECT, OK, or ERROR result code.
If no more data is in the transmit buffer, and the last transmitted character was not
an ASCII NULL, the modem generates the OK result code and returns to the
command mode. If the last character transmitted was an ASCII NULL, the modem