RC224ATL/224ATLV
6.0 Operation
EmbeddedModem Family
6.2 Fax Modes
Each frame is checked to see if the current frame is the last frame of the
transmission. If the final frame bit (5th received bit of the second byte of the
frame) is 1, indicating that the current frame is the final frame, the modem
completes the frame transmission, issues the OK result code, and returns to the
command state. If the final frame bit is a 0, the modem issues the CONNECT
result code and continues to transmit flags until one of the following actions is
taken by the DTE:
1. If additional data is sent by the DTE, the modem transmits another frame.
2. If the transmission is terminated by the <DLE> <ETX> string, the modem
turns off the carrier and issues the OK result code.
3. If no data is sent by the DTE within 5 seconds of receiving the CONNECT
message, the modem turns off the carrier and issues the ERROR result
code.
6.2.8 Fax Control Reception
Fax control reception is initiated by the +FRH command or after dialing. Upon
recognition of the command, the modem initiates the selected demodulation mode
and looks for the proper carrier. When the selected carrier is detected, the modem
issues the CONNECT result code. If a signal other than the selected carrier is
detected, the modem issues an +FCERROR result code and returns to the
command state.
The modem removes the flags, removes transmitter inserted 0 bits (a 0
following five consecutive 1s), performs the CRC error checking, and stores the
data in the internal I/O buffer for further processing and eventual passing to the
DTE.
The modem indicates the end of a frame by issuing the <DLE> <ETX>
characters and an OK result code if the frame was received correctly, or by issuing
an ERROR result code if one or more errors were detected in the frame. The first
frame received is stripped of flags (CONNECT result code indicates that a valid
flag has been received) and output to the DTE. Subsequent frames are buffered
and output to the DTE when additional +FRH commands are received.
Any characters other than flow control that are received while demodulating
data and prior to issuance of the status result code will result in the receive
process being aborted, an OK result code being issued, and the modem returning
to the command state. After the status result code is issued, the modem continues
to demodulate data. Additional +FRH commands specifying the same modulation
rate will result in the issuance of a CONNECT result code, output of the next data
frame, and continuation of normal demodulation. Any other commands will result
in the receive process being aborted, buffered data being discarded, and the
command being implemented.
Detection of loss of carrier will result in the modem issuing the NO
CARRIER result code and returning to the command state.
6.2.9 Fax I/O Processing
The fax I/O interface supports asynchronous serial and parallel interfaces. The
interface rate is 19.2 kbps. Start and stop elements are removed from the
incoming serial data stream and are added to the outgoing serial data (receive).
D224ATLVDSC
Conexant
6-5
CONEXANT [ CONEXANT SYSTEMS, INC ]
