Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 226)

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AT+F1 Enable B103 Receiver for Data Block
reception. Modem enables FSK receiver, waits for >12T marks
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-
nel command. Transmit Space for 600 ms, followed by Mark for
180 ms. Then send CONNECT to DTE to indicate
modem is ready to accept data.
AT+F6 Abort current Data Block Reception or
Transmission. This command is useful for exception handling,
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.
Table 142. AT Commands Provided to Support SIA Level-3 Protocol Communication (Continued)
AT Command Modem Function Remarks