Intel MD566X 6.1 DTMF Detection , 6.2 Relay Control

56K V.92 Data, Fax, and Voice Chipset

Programmer’s Guide Intel Confidential 81

6.1 DTMF Detection

DTMF detection information is handled differently than other detection information. IS-101

specifies that more than one <DLE><DTMF CHAR> character pair may be sent for a single DTMF

tone burst. As such, the modem sends delimiter <DLE> character pairs to indicate the end of a tone

burst. When a DTMF tone is detected in playback or command mode, the modem sends

<DLE><DEL> to indicate the end of a burst. For example, from a single burst of DTMF5 tones, the

following reports are possible:

Playback and voice command modes:

When a DTMF tone is detected in the record mode, the modem sends <DLE></> to indicate the

beginning of a tone burst. The modem may then send one or more <DLE><DTMF CHAR> character

pairs followed by <DLE><DEL>, which signifies the end of the tone. For example, from a single

burst of DTMF 5 tones, the following reports are possible:

Record mode only:

[voice data]<DLE></><DLE><5>[voice data ]<DLE><DEL>[voice data]

[voice data]<DLE></><DLE><5>[voice data]<DLE><5>[voice da-

ta]<DLE><DEL>[voice data]

6.2 Relay Control

To originate a call (that is, to originate call forwarding or auto-dialing) and to generate tones, use

the dialing command:

ATDT <telephone number>

If the modem was not already off-hook, then this command automatically configures the value for

AT+V LS= n to n=1 or n=5 depending on the value for Mn.

To answer a call, use the AT+VLS =n command. Unlike data mode, the modem (when configured

for voice mode) does not automatically answer an incoming call (that is, the modem ignores the

contents of S-register S0).

Remote playback/record takes place whenever the modem is off-hook (OHREL* is activated). For

local playback/record, the modem is on-hook, and the user uses a local telephone or handset. The

LPHREL* relay driver may be used to control the local telephone or handset when implementing

local playback/record mode (AT+VL S=n). Additionally, voice messages may be played through

the modem/computer speaker. The FastPath chipsets also provide a microphone interface that can

be used for local recording.

In voice mode, all voice AT commands can be issued by the DTE at any valid speed between 300

bps to 115,200 bps. Typically, the DTE-to-modem data rate is set for 19,200 bps, which is the

recommended data rate for Class 1 fax mode. The DTE-to-modem data rate may need to be set to

115,200 bps in certain instances, such as during playback or during record mode for a CL1

compression scheme.

The following data and fax AT commands are supported in voice mode:

Data: All except ATA, ATIn

Fax: +FCLASS