<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.