Silicon Laboratories SI2493/57/34/15/04, SI2494/39 manual AT+F1, AT+F2, AT+F3, AT+F4, AT+F5, AT+F6

AN93

Table 142. AT Commands Provided to Support SIA Level-3 Protocol Communication (Continued)

AT Command	Modem Function	Remarks
AT+F1	Enable B103 Receiver for Data Block	Modem enables FSK receiver, waits for >12T marks
	reception.	to be detected, then sends CONNECT message to
		DTE to indicate a received Data Block follows.
		Modem will stay in this mode indefinitely until an AT
		command is issued by DTE. It is usually a
		+F3(ACK), +F4(NACK) or +F5(ACK followed by
		Data Block transmission) command.
		Note1: Modem will wait for up to 1 second to detect
		>12T marks before unclamping RXD. After 1 sec-
		ond RXD will be unclamped regardless.
		Note 2: The +F1 command can be used to resume
		SIA protocol communication after a voice listen-in or
		V.32bis interruption.
AT+F2	Enable tonal ACK/NACK detection.	Detect and report ACK or NACK to DTE.
		‘OK’ for ACK and ‘ERROR’ for NACK.
		A NACK will be reported if no valid signal is
		detected within 2.5 seconds.
AT+F3	Transmit Tonal ACK	Transmit Space for 600 ms. Send ‘OK’ prompt to
		DTE when done.
AT+F4	Transmit Tonal NACK	Transmit Mark for 600 ms. Send ‘OK’ prompt to
		DTE when done.
AT+F5	Transmit Tonal ACK with reverse chan-	Transmit Space for 600 ms, followed by Mark for
	nel command.	180 ms. Then send CONNECT to DTE to indicate
		modem is ready to accept data.
AT+F6	Abort current Data Block Reception or	This command is useful for exception handling,
	Transmission.	such as timeout. If the FSK transmitter was on, +F6
		shuts it off. FSK reception is aborted and modem
		returns to the AT command mode.

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