Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 151)

AN93
Rev. 1.3 151
6.5. 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 ISOmodem 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 are received.
The CWCID data are 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 99 defines the Multiple Data Message Format (MDMF) parameters in the example response.
The SAS tone varies between countries and requires configuration of user registers U9F to UA9. The SAS_FREQ
(U9F) register sets the expected SAS tone frequency as shown in Table 100. The default SAS frequency is 440 Hz.
The expected cadence is set in cadence registers SAS_CADENCE0 (UA0) through SAS_CADENCE9 (UA9).
Table 99. MDMF Parameters
Character Description Hexadecimal Value ASCII Value
Message Type (MDMF) 80
Message Length 20
Parameter Type (Date/Time) 01
Parameter Length 08
Month 30 39 09
Day 31 31 11
Hour 31 36 16
Minutes 32 31 21
Parameter Type (Number) 02
Parameter Length 0A
Number 35 31 32 35 35 35 31 32 33 34 5125551234
Parameter Type (Name) 07
Parameter Length 08
Name 4A 4F 48 4E 5F 44 4F 45 JOHN_DOE
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