Specifications

AN93
112 Rev. 0.9
To transmit Protocol 1 or Protocol 2 data, the host must
send “AT+FTM = 201” or “AT+FTM = 202”. This causes
the modem to return to data mode and wait silently until
data is received from the host processor for
transmission. Once data is received from the host, the
modem transmits the proper number of channel seizure
and mark bits followed by the data it received from the
host. After the modem has begun transmitting, it will
send marks when it does not have data to send and will
continue to do so until the host escapes to command
mode.
The content of the data message is entirely up to the
host including any checksum or CRC. ETSI ES 201 912
describes two standard data and transfer layers that are
commonly used. SMS typically relies on caller
identification information to determine if the call should
be answered using an SMS device or not. Refer to
"3.5.20.3. Caller ID" on page 139 for more information
on how to configure the modem for caller ID detection.
3.5.4. Type II Caller ID/SAS Detection
When a call is in progress, the Subscriber Alerting
Signal (SAS) tone is sent by the central office to indicate
a second incoming call. The central office may also
issue a CPE Alert Signal (CAS) after the SAS to indicate
that call waiting caller ID (CWCID) information is
available. If properly configured, the modem will
acknowledge the CAS tone, receive the CWCID data,
and perform a retrain.
The Si24xx is configured through the +PCW command
to toggle the RI pin (+PCW=0), hang up (+PCW=1), or
do nothing (+PCW=2) upon receipt of the SAS tone.
The default is to ignore the SAS tone. The modem,
enabled through the +VCID command, will collect caller
ID information if +PCW is set to toggle the RI pin. The
AT:I command can be used to verify receipt of the SAS
and CWCID data. Bit 9 will be set for SAS receipt due to
the RI toggle. Bit 4 will be set if CWCID data is received.
The CWCID data is collected using the +VCIDR?
command. The data message is displayed in
hexadecimal format using ASCII text. The modem will
return “NO DATA” if no caller ID is available. The
+VCIDR response is listed below for the following
example CWCID message:
Date & Time: 09/11 16:21
ICLID Number: 512-555-1234
Calling Name: JOHN_DOE
+VCIDR:
80 20 01 08 30 39 31 31 31 36 32 31 02 0A 35 31
32 35 35 35 31 32 33 34 07 08 4A 4F 48 4E 5F 44
4F 45 40
OK
Table 80 defines the Multiple Data Message Format (MDMF) parameters in the example response.