Silicon Laboratories SI2494/39 manual Type II Caller ID/SAS Detection, Mdmf Parameters, Johndoe

AN93

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.

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
Checksum	40

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).

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