<DLE>-SHIELDED CODES
In voice transmit/receive mode, BISYNC protocol should be applied to the data stream to/from the DCE. During this period, commands and responses will be in <DLE> shielded form. The supported <DLE> shielded codes are as follows (all <DLE> shield codes are case sensitive):

COMMANDS 
  Code          Simple Action Command Description
-------         --------------------------------------------------
 <NUL>          This is something I would recommend
 <DLE>          Complies with IS-101
   p            Pause Transmit Data State("Immediate Command").
		Complies with IS-101
   r            Resume Transmit Data State("Immediate Command").
		Complies with IS-101
 <ETX>          End Transmit Data State ("Stream Command").
		Complies with IS-101.
 <CAN>          Clear transmit buffer of voice data("Immediate Command").
		Complies with IS-101.
 <FS>or<DC2>    Concatenate transmit data streams("Stream Command").
		Complies with IS-101.
 <DC4>          Clear transmit buffer of voice data and return to command
		mode("Immediate Command"). Not defined in IS-101.

RESPONSES 
  Code             Event Report Description
-------            --------------------------------------------------
 <DLE>              Two contiguous <DLE><DLE> codes indicate a single
		    <DLE> in the data stream. Complies with IS-101
 <ETX>              End Data State. Complies with IS-101
   0                DTMF '0' received. Complies with IS-101
   1                DTMF '1' received. Complies with IS-101
   2                DTMF '2' received. Complies with IS-101
   3                DTMF '3' received. Complies with IS-101
   4                DTMF '4' received. Complies with IS-101
   5                DTMF '5' received. Complies with IS-101
   6                DTMF '6' received. Complies with IS-101
   7                DTMF '7' received. Complies with IS-101
   8                DTMF '8' received. Complies with IS-101
   9                DTMF '9' received. Complies with IS-101
   #                DTMF '#' received. Complies with IS-101
   *                DTMF '*' received. Complies with IS-101
   c                T.30 Facsimile Calling Tone. Complies with IS-101
   e                Data Calling tone. Complies with IS-101
   s                "Presumed Hangup"(Silence) Time-out.
		    Silence detected. The DCE has determined that there
		    was no voice energy present at the the beginning of
		    the voice recording session followed by a period of
		    silence greater than the amount of time selected by
		    AT+VSD command. Complies with IS-101
   q                "Presumed End of Message" (Quiet) Time-out.
		    Quiet detected. The DCE has determined that there was
		    voice energy present at the the beginning of the voice
		    recording session followed by a period of silence
		    greater than the amount of time selected by AT+VSD
		    command. Complies with IS-101
   b                Busy tone. Complies with IS-101
   d                Dialtone tone. Complies with IS-101.

DESCRIPTION

DTE to DCE stream. The DCE will filter the data stream from the DTE and remove all character pairs beginning with <DLE>. The DCE will recognize <DLE><DLE> and reinsert a single <DLE> in its place. The DTE must filter stream data to the DCE, and insert extra <DLE> characters ahead of <DLE> data.

+--------------+ | TDA=Tx Data | +--------------+ | +------------+ | TDA=DLE ? | +------------+ | +--------------------+ YES| |NO +--------------+ +--------------+ | Send two DLE | | Sned TDA to | | to UART | | UART | +--------------+ +--------------+ DCE to DTE stream. The DTE must filter the data stream from the DCE and remove all character pairs beginning with <DLE>. The DTE must recognize <DLE><ETX> as the stream terminator. The DTE must recognize the <DLE><DLE> and reinsert a single <DLE> in its place. The DCE will filter stream data to the DTE, and insert extra <DLE> characters ahead of <DLE> data.

+--------------+ | RDA=Rcv Data | +--------------+ | +------------+ | PREVDLE=1? | +------------+ | +---------------------------+ YES| |NO +-----------+ +-----------+ | PREVDLE=0 | | PREVDLE=0 | +-----------+ +-----------+ | | +----------+ +-----------+ | RDA=DLE? | | RDA=DLE ? | +----------+ +-----------+ | | +-----------+ +-----------------+ YES| |NO YES| |NO +----------+ +-----------+ +-----------+ +-----------------+ | Put RDA | | Check for | | PREVDLE=1 | | Is it Tx mode ? | | into Buf | | Command | +-----------+ +-----------------+ +----------+ +-----------+ |YES +-------------------+ | Check if XON/XOFF | +-------------------+ | +--------------+ YES| |NO +-----------+ +----------+ | Handle | | Put RDA | | Flow Cntl | | into Buf | +-----------+ +----------+

Examples of voice mode operation.
ZyXEL Advanced Voice Capability.

Sam Leffler / sam@engr.sgi.com. Last updated $Date: 1995/02/20 01:24:15 $.