class_1.txt

传真编程的一些文档

                   SUPRA TECHNICAL SUPPORT BULLETIN 
               CLASS 1 FAX COMMANDS FOR SUPRA FAXMODEMS 
                              6/19/92
Supra Corporation
7101 Supra Drive SW, Albany, OR  97321
General [phone] / Sales [phone] / Fax [phone]
Supra Tech Support  [phone]  8:00am - 5:00pm PST, M-F

Supra BBS........[phone]  24 Hours
CompuServe.......76004,565
BIX..............SupraCorp
America Online...SupraCorp2
GEnie............SupraTech
AppleLink........D2456
UseNet [e-mail]
            .....supra![e-mail]

SUPRA's DISCLAIMER:
   The following information has been taken from Rockwell's RC144AC 
manual. It has not been taken from the CCITT Class 1 documentation, 
which is copyrighted by the CCITT.  This information is provided for 
educational purposes only.  To fully understand this information 
requires a through knowledge of the T.4 fax image and the T.30 fax 
session protocol standards.  Due to the nature of this information, 
Supra's engineers and technical support can not and will not provide any 
help or support on this information.  We STRONGLY urge anyone attempting 
to develop fax software to get the required documentation from Global 
Engineering or the TIA.

SHORT HISTORY OF CLASS 1 AND 2
  In 1988 the CCITT TR29.2 committee accepted the Class 1 standard for 
communication between fax software and fax modems.  The committee also 
voted on, but did not accept for various technical reasons, the Class 2 
standard.  A year later, they had slightly revised the standard but 
again did not accept it.  Software and hardware manufactures decided to 
unofficially adopt this standard until the TR29.2 committee could 
develop an acceptable standard.  Since so many companies have used the 
unofficial standard, the TR29.2 committee has designated that when the 
standard is officially adopted it will be known as Class 2.0.  Over the 
last year or so, the TR29.2 committee has voted on several revisions to 
the Class 2 standard.  Their last vote was early May '92.  A no vote for 
technical reasons was entered.  The TR29.2 committee is now reviewing 
the technical issues that were raised.  At this time, Supra has not 
heard of a projected date for the next ballot.

WHAT IS THE DIFFERENCE BETWEEN CLASS 1 AND 2
  Class 1 fax software handles all of the T.4 fax image and T.30 session 
protocol information and timing.  Thus, the ability to communicate 
properly with various fax machines is more a function of the software 
than the fax modem.  Class 2 fax software generates a T.4  fax page 
image and sends it to the fax modem a page at a time.  The fax modem 
then handles the T.30 session protocol information and timing.  This 
relieves the computer's cpu from some work.  The ability to communicate 
properly with various fax machines is more a function of the fax modem 
than the software.  However, to further complicate matters, class 2 fax 
software can issue Class 1 commands and take over some of the duties of 
the Class 2 fax modem.  

  When customers have a problem communicating correctly with a fax 
machine/modem, it can be very difficult to determine which is at fault,
 the software or the hardware.  Supra has collected numerous Class 1 and 
2 fax software for a variety of different computers.  When we receive a 
report of a problem, we use these programs to determine if it is a 
software or hardware problem.  If it is a hardware problem, we notify 
Rockwell, otherwise we notify the software company.

BUG REPORTS
  Supra is dedicated to making the best product for the best price.  If 
you feel that you have found a bug, please fax or send a letter to the 
attention of:

   SUPRA V32/BIS FAX BUG

Please fully describe the 'bug' (specific steps to generate it, phone 
numbers to call, make and model of fax/modem, rev of our ROM (from I3 
command) ), why you believe that it is a bug, what specific section of 
Class 2 applies to this bug and how you would like the bug to be fixed.  
Please remember that there are issues that have not been addressed or 
settled by the TR29.2 committee in the Class 2 specifications. (i.e. how 
the DCD and DTR lines are handled while in fax mode.)


WHERE TO GET OFFICIAL FAX DOCUMENTATION

  Telecommunications Industry Association
  1722 Eye St. NW
  Suite 440
  Washington, DC  20006

You need to ask for:

    Class 1 documentation - EIA/TIA-578
    Class 2 documentation - Electronic Industries Association and 
Telecommunications Industry Association TIA Project Number 2388, 
Asynchronous Facsimile DCE Control Standard, Service Class 2, TR-29.2 
Committee Letter Ballot

  Global Engineering Documents                     
  2805 McGaw Ave
  Irvin, CA  92713 
  800-854-7179
  714-261-1455
  714-261-7892 (Fax)     

You need to ask for:

    EIA/TIA-578 - Class 1 documentation
    EIA/TIA-592 - Class 2 documentation
    CCITT v7.3  - T.1 - T.90 standards, includes T.4 & T.30

(The cost for the above docs will run close to $200.  But Global will 
also update you on any changes or additions to those standards you 
purchase.)

Global Engineering will not have the Class 2 documentation until approx. 
a month after the TR29.2 committee accepts it.  Most of those companies 
which have developed Class 2 fax software either sit on the TR29.2 
committee or know someone who does.  It may be possible to receive the 
documentation from the TIA if you present a credible proposal.  Supra 
has no knowledge of what this proposal should consist of or who you need 
to talk to.


See also "CLASS 1 FAX COMMANDS FOR SUPRA FAXMODEMS" which is available
on Supra BBS.



6 FAX CLASS 1 OPERATION

6.1  FAX I/O PROCESSING

The fax I/O interface supports asynchronous serial and parallel 
interfaces.  The interface rate is 19200 bps.  Start and stop elements 
are removed from the transmit data and added to the receive data.  Both 
transmit and receive data is buffered.  Flow control using XON/XOFF 
(DC1/DC3) or RTS/CTS is provided.

Unique control character strings are identified, filtered, or reinserted 
into the I/O data stream.  These control characters and their resultant 
action are described below.

6.1.1 DTE TO MODEM TRANSMIT DATA STREAM

Characters Detected       Action taken

<DLE><data>               Delete <DLE><data> characters

<DLE><ETX>                Recognize as a string terminator, and take 
                          appropriate action

<DLE><DLE>                Replace with single <DLE> character

6.1.2 MODEM TO DTE RECEIVE DATA STREAM

Characters Detected     Action taken

<DLE>                   Insert extra <DLE> ahead of <DLE>

The modem also identifies the end of a frame by inserting <DLE><ETX> 
into the data stream after the FCS bytes.

6.1.3  FAX MODE SELECTION

Fax class 1 commands are identified in Table 6-1 and defined in Table 6-
2.  Fax modes and rates are determined by the AT+F commands as described 
in Table 6-2.

6.1.4  FAX ORIGINATION

Origination of fax calls is made using the ATD command.  Upon completion 
of the dial function, a calling tone at 1100 Hz, with a cadence of 0.5 
seconds ON, and 3 seconds off is transmitted.  The modem automatically 
enters mode +FRH=3 and sends the CONNECT message to the DTE when FSK 
flags are detected from the remote.

6.1.5  FAX ANSWERING

Answering of fax calls is identical to answering of data calls with the 
exception that the modem enters the fax handshaking mode instead of the 
data handshaking mode after going off-hook.  If +FAE=0, the modem , 
after sending answer tone, automatically enters fax mode (+FTH=3), sends 
the CONNECT message to the DTE, and starts sending FSK flags.  If 
+FAE=1, the modem determines if the caller is a data modem or fax modem 
and sends the DATA or FAX result code, respectively, to the DTE.

Table 6-1.  Fax Class 1 Commands

-----------------------------------------------------------
|   Command        Function                               |
|---------------------------------------------------------|
|   SERVICE CLASS ID                                      |
|---------------------------------------------------------|
|   +FCLASS=       Service Class                          |
|---------------------------------------------------------|
|   FAX CLASS 1 COMMANDS                                  |
|---------------------------------------------------------|
|   +FTS=n         Stop Transmission and Wait             |
|   +FRS=n         Receive Silence                        |
|   +FTM=n         Transmit Data                          |
|   +FRM=n         Receive Data                           |
|   +FTH=n         Transmit Data with HDLC Framing        |      
|   +FRH=n         Receive Data with HDLC Framing         |
|---------------------------------------------------------|


6.1.6  FAX CONTROL TRANSMISSION

Fax control transmission is initiated by the AT+FTH=n command.  After 
this command is issued, the modem generates the CONNECT message and 
transmits carrier in the modulation scheme specified by the parameter n.  
The modem then transmits HDLC flags for a minimum of 1 second.  The 
modem continues to transmit the HDLC flags until it receives a character 
from the DTE.

When characters are received from the DTE, the modem adds start and end 
flags, performs zero-bit insertion, generates FCS, and deletes 
<DLE><chr> character pairs before transmitting the characters to the 
remote fax machine.  Each <DLE><DLE> sequence is transmitted as a single 
<DLE>.  <DLE><ETX> is considered as the end of frame marker and is not