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536EX Chipset Developer’s Manual 69
Intel Confidential
Fax Class 1 AT Commands
+FTH=m none
Transmit HDLC Data: The +FTH=<mod> command causes the modem to transmit
data framed in HDLC protocol using the modulation mode selected. <mod> may have
the values shown in Table 23 on page 65.
After receiving the +FTH command, the modem sends a ‘CONNECT’ result code to
the DTE. The modem then transmits signal converter training (if required) followed by
flags until the first byte of data is sent by the DTE. The modem terminates the +FTH
command upon detecting <DLE><ETX> characters in the data stream.
When the buffer is empty, the modem computes and appends the FCS (Frame Check
Sequence) and a closing flag to the frame. The modem ensures that the minimum
number of flags required by T.30 are sent before the data from the DTE begins to be
transmitted.
The modem checks the final frame bit in the control field of each frame; this is the fifth-
received bit of the second byte of each frame. If the final frame bit is a ‘1’, the modem
ceases transmission after the frame is sent, returns to command state, and sends the
‘OK’ result code to the DTE. If the final frame bit is a ‘0’, the modem sends another
‘CONNECT’ result code to the DTE after the current frame is sent. The modem
continues to transmit flags until the DTE takes one of the following actions:
• The DTE sends additional data. The modem then transmits another frame.
• The DTE sends only <DLE><ETX> (a null frame). The modem then turns off the
transmit carrier and send the ‘OK’ result code to the DTE.
• If the DTE transmits no additional data within 5 seconds from when the modem
reported the ‘CONNECT’ result code, the modem turns off the transmit carrier
mode, returns to command mode, and sends the ‘ERROR’ result code to the DTE.
In HDLC transmit mode, the modem performs HDLC transparency functions, FCS
generation, and buffers the transmit data. The modem uses the configured method of
flow control to pause the DTE as necessary.
NOTE: If the modem is on-hook, it always returns an ‘ERROR’ message to the DTE
after receiving the +FTH=<mod> command.
Range: <mod> = 3
Refer to Table 23 on page 65.
+FTM=m none
Transmit Data: The +FTM = <mod> command causes the modem to transmit data
using the modulation selected in <mod>.
The modem returns a ‘CONNECT’ result code and transmits the proper training
sequence in the selected mode, followed by constant ‘1’ bits until data is received from
the DTE. The modem terminates this command upon detecting <DLE><ETX>
characters in the data stream.
If the modem’s transmit buffer empties and the last transmitted character is an ASCII
NULL (00), the modem continues to transmit NULLs until the DTE sends more data or
5 seconds have elapsed. After 5 seconds have elapsed with an empty transmit buffer,
the DCE turns off the transmit carrier, returns to command state, and returns an
‘ERROR’ result code to the modem.
NOTE: Hex $00 replication does not provide the required timing needed for
generating the TCF frame (1.5 seconds of ‘0’s’).
If the modem’s transmit buffer empties and the last transmitted character was not a
NULL, the modem turns off the transmit carrier, returns to command state, and sends
the ‘OK’ result code to the DTE.
NOTE: If the modem is on-hook, the modem always returns an ‘ERROR’ message to
the DTE after receiving the +FTM = <mod> command.
Range: <mod> = 24, 48, 72, 73, 74, 96, 97, 98, 121, 122, 145, 146
Refer to Table 23 on page 65.
+FTS=m none
Stop Transmission and Pause: The +FTS=<TIME> command causes the modem to
stop all transmissions. The modem waits for the specified amount of time, then sends
an ‘OK’ result code to the DTE. The value <TIME> is in 10 ms intervals.
Range: <TIME> = 0–255 (in 10 ms intervals)
Table 24. Fax Mode Command Descriptions (Continued)
Command Default Description
NOTE: An asterisk (*) denotes the factory-default setting.