class_1.txt

传真编程的一些文档

transmitted.  All data received from the DTE afar <DLE><ETX> is ignored 
by the modem until the modem generates either the CONNECT, OK, or ERROR 
result code.

If no more data is in the transmit buffer and the final bit was a 1 (bit 
4 of the second byte received from the DTE), the modem generates the OK 
result code and returns to the command mode.  If the final bit was a 0, 
the modem generates the CONNECT message and waits for further data from 
the DTE while transmitting HDLC flags.  If no more data is received 
before 5 seconds elapse, the modem drops carrier, goes on-hook, and 
generates the ERROR result code.

6.1.7  FAX CONTROL RECEPTION

Fax control reception is initiated using the AT+FRH=n command.  After 
this command is issued, the modem looks for carrier in the modulation 
scheme specified by the parameter n.  If no carrier is detected before 
the period of time specified by register S7 expires, the modem generates 
the NO CARRIER message and returns to command mode.  If carrier is 
detected that is not the one specified by the parameter n, the modem 
generates the +FCERROR message and returns to the command mode.  If the 
specified carrier is detected, the modem generates the CONNECT message 
and enters the HDLC receive mode.

In HDLC receive mode, the modem receives HDLC frames from the remote fax 
machine, strips the flags, performs zero-bit deletion, performs error 
checking, and handles <DLE><chr> character pairs before passing the data 
to the DTE.  The modem prefixes each <DLE> character with another <DLE> 
character before sending it to the DTE.  After the last byte in the 
frame, the modem sends <DLE><ETX> to the DTE marking the end of the 
frame.  The modem then generates either the OK message if errors were 
detected (FCS is incorrect), and returns to command mode.

While in command mode, the modem continues to receive data in the 
selected modulation scheme, and sends the data after sending the CONNECT 
message to the DTE when the DTE reissues the +FRH command with the same 
parameter.  If the DTE issues the +FRH command with a different 
parameter, the modem clears all buffers and proceeds as described 
previously.

If carrier is lost while in command mode and the DTE reissues the +FRH 
command with the same parameter, and there is no data in the buffer, the 
modem sends the ERROR result code to the DTE and returns to the command 
mode.  If there is data in the buffer, the modem sends the next frame of 
buffered data to the DTE, followed by <DLE><ETX>, and either the ERROR 
result code if errors were detected or the OK result code if no errors 
were detected.  The modem then returns to command mode.

The modem concludes an error is detected if the carrier is lost for any 
period of time during or before the reception of a frame.  If carrier is 
lost for a time period longer than the time specified by the register 
S10, the modem finishes delivering the data in the receive buffer (if 
any) to the DTE, sends <DLE><ETX>, generates the ERROR message, and 
returns to command mode.  All subsequent data received from the remote 
is discarded.

If the modem detects a frame abort sequence (seven consecutive ones with 
no zero insertion) while it is waiting for a frame beginning flag (it 
was receiving HDLC flags), it will wait for the HDLC flags again until 
either carrier is lost, or the DTE aborts the process by sending an 
abort character or by dropping DTR with &D2 in effect.  If the frame 
abort sequence is detected while the modem is receiving a frame it 
finishes delivering the data in the receive buffer (if any) to the DTE, 
sends <DLE><ETX>, generates the ERROR message, and returns to command 
mode.  The modem keeps looking for HDLC flags followed by more data from 
the remote, with the selected modulation scheme.

If the modem detects a receive buffer overflow condition, it concludes 
that there was a FCS error in that frame.  The modem will receive more 
frames only if a starting flag is detected and there is room in the 
receive buffer.  If a starting flag is detected and there is no room in 
the buffer, the modem discards all data in that frame.

If the modem receives any character from the DTE after the +FRH command 
(except flow control characters if software flow control is in effect), 
or if the modem detects a high-to-low transition of the DTR signal while 
&D1 is in effect, it sends <DLE><ETX> to the DTE, generates OK result 
code, and returns to command mode.  The receive buffer is cleared and 
all data received from the remote is discarded.  If the modem detects a 
DTR drops while &D2 is in effect, it goes on-hook, sends <DLE><ETX> to 
the DTE, generates OK result code, and returns to command mode.  If the 
modem detects a DTR drop while &D3 is in effect, the modem performs a 
warm reset.

6.1.8  FAX DATA TRANSMISSION

Fax Data transmission is initiated by the AT+FTM=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 constant 1 bits for a minimum of one second and 
continues to transmit constant 1 bits until it receives a character from 
the DTE.

When data is received from the DTE, the modem deletes start and stop 
bits and deletes all <DLE><chr> character pairs before transmitting the 
data to the remote.  Each <DLE><DLE> sequence is transmitted as a single 
<DLE>.  <DLE><ETX> is considered as the end of stream marker, and is not 
transmitted.  All data received from the DTE after the <DLE><ETX> is 
ignored by the modem until the modem generates either the CONNECT, OK or 
ERROR result code.

If no more data is in the transmit buffer, and the last transmitted 
character was not an ASCII NULL, the modem generates the OK result code 
and returns to the command  mode.  If the last character transmitted was 
an ASCII NULL, the modem generates the CONNECT message to the DTE and 
waits for further data from the DTE while transmitting NULLs to the 
remote.  If more data is received before five seconds, elapse, the modem 
continues to transmit the data as described in the previous paragraph.  
If five seconds elapse and no data is received from the DTE, the modem 
drops carrier, goes on-hook, and generates the ERROR result code.

6.1.9  FAX DATA RECEPTION

Fax data reception is initiated using the AT+FRM=n command.  After this 
command is issued, the modem looks for carrier in the modulation scheme 
specified by the parameter n. If no carrier is detected before the 
period of time specified by register S7 expires, the modem generates the 
NO CARRIER message and returns to command mode.  If carrier is detected 
that is not the one specified by the parameter n, the modem generates 
the +FCERROR message and returns to the command mode.  If the specified 
carrier is detected, the modem generates the CONNECT message and enters 
the data receive mode.

While in data receive mode, the modem receives data from the remote, 
adds start and stop bits, and handles <DLE><chr> character pairs before 
passing the data to the DTE.  The modem prefixes each <DLE> character 
with another <DLE> character before sending it to the DTE.

If carrier is lost for a time period longer than the time specified by 
the register S10, the modem finishes delivering the data in the receive 
buffer (if any) to the DTE, sends <DLE><ETX>, generates the NO CARRIER 
result code, and returns to the command mode.  All subsequent data 
received from the remote is discarded.

If the modem detects a receive buffer overflow condition, it stops 
receiving from the remote until there is room in the receive buffer.  
The modem informs the DTE of the buffer overflow after it sends to the 
DTE the last character that was stored in the buffer before the overflow 
occurred.  

If the modem receives any character from the DTE after the +FRM command 
(except flow control characters if software flow control is in effect), 
or if the modem detects a high-to-low transition of the DTR signal while 
&D1 is in effect, it sends <DLE><ETX> to the DTE, generates the OK 
result code, and returns to command mode.  The receive buffer is cleared 
and all data received from the remote is discarded.  If loss of DTR is 
detected while &D2 is in effect, the modem goes on-hook, sends 
<DLE><ETX> followed by OK result code to the DTE, and returns to command 
mode.  If the modem detects a DTR drop while &D3 is in effect, the modem 
performs a warm reset.

6.2  EXAMPLES

Examples of calling (transmitting) and answering (receiving) one page 
use fax class 1 commands are shown in Tables 6-3 and 6-4, respectively.

Table 6-2.  Fax Class 1 Command Definitions

Command         Description

+FCLASS=n     Select service class.  +FCLASS=n command set the active 
                service class
                Parameters: 0-2
                  Default: 0
                Command options:
                  +FCLASS=0    Select Data Mode
                  +FCLASS=1    Select Facsimile class 1
                  +FCLASS=2    Select Facsimile class 2

+F<command>?  Report Active Configuration.  +F<command>? interrogates 
              the modem to determine the active configuration.  Typical 
              responses are:
                +FAE?     0 if autoanswer is disabled, 1 if auto answer 
                          enabled.
                +FCLASS?  0 if in data mode; 1 if in fax class 1; 2 if 
                          in fax class 2

+F<command>=?  Report Operating Capabilities.  +F<command>=? can be used 
               to determine the operating capabilities of the modem.
               Typical responses are:
                 +FAE=?    0,1
                 +FCLASS=? 0,1,2
                 +FTM=?    3,24,48,72,96 (RC96AC)
                 +FRM=?    3,24,48,72,96 (RC96AC)
                 +FTM=?    3,24,48,72,73,74,96,97,98,121,122,145,146 
                           (RC144AC)
                 +FRM=?    3,24,48,72,73,74,96,97,98,121,122,145,146 
                           (RC144AC)

+FAEn          Data/Fax Auto Answer.  +FAEn allows the DTE to either 
               restrict answering to class 1, or to automatically detect 
               whether the calling station is a fax class 1 modem or 
               data modem,, and answer accordingly.

               Parameters: 0,1
                   Default:0
               Command options:
                   n=0      Disable data/fax auto answer mode (default). 
                            The modem answers as a fax modem only
                   n=1      Enable data/fax auto answer mode.  The modem 
                            answers as a fax or data modem

+FTS=n         Stop Transmission and Wait.  +FTS=n causes the modem to 
               terminate a transmission and wait for n 10 millisecond 
               intervals before responding with the OK result code.  An 
               ERROR response code results if this command is issued 
               while the modem is on-hook.

+FRS=n         Receive Silence.  +FRS=n causes the modem to report back 
               to the DTE with an OK result code after n millisecond 
               intervals of silence have been detected on the line.  
               This command is aborted if any character is received from 
               the DTE.  The modem discards the aborting character and 
               issues an OK result code.  An ERROR response code results 
               if this command is issued while the mode is on-hook.

+FTM=n        Transmit Data.  +FTM=n causes the modem to transmit data 
              using the modulation defined below.  An ERROR response 
              code results if this command is issued while the modem is 
              on-hook.

              Parameters: