Comtrol AT Commands - Manual (Page 61)

AT Commands for CX81801/CX06833/CX81300/CX06827 Modems Reference Manual
102184B Conexant 3-35
Entering and Exiting In Band Active State
In Band Command mode will be active only when a modem connection has been made
and DCD is on and the modem is not in command mode. Upon a data connection before
the connect message is sent, an In Band message will be sent to the DTE to notify that all
further data will be EM shielded and should be filtered. Any other time (i.e., command
mode or idle mode) the DTE should allow all user data to be in pass-through mode in
which the data is unfiltered.
The DTE will receive one of the following active messages:
EM<60h><26h><62h>+IBC:1 to indicate In Band is active and the server is V.92
EM<60h><26h><62h>+IBC:2 to indicate In Band is active and the server is non-V.92
Upon Hang up or escape to command mode, the In Band command mode will end and
the DTE should stop filtering EM data and return to pass-through mode.
The DTE will receive the following inactive In Band message:
EM<60h><26h><62h>+IBC:0 to indicate In Band is inactive
EM Shielding Data
When in-band control sequences are enabled, the DTE and the modem must shield and
filter data containing EM. In V.80, in-band data is shielded from normal data by an EM
character represented by a <19h> or <99h>. If the DTE’s data contains an EM, an
additional character is inserted.
For example, sending <19h> from the DTE to the modem requires inserting a
<singleEM> or <5Ch> into the data stream (e.g., <19h><5Ch>). The modem encodes
this as one <19h> in the user data. On the other hand, sending <19h> from the modem to
the DTE requires inserting a <singleEM> or <7Ch>. See Table 3-3. Please refer to the
V.80 standard for more information.
Table 3-3. Supported V.80 Commands
Command Hex Codes Description
Supported V.80 DTE-to-DCE Commands
<extend0> <length>
<control> <rest of command> <40h>
<42h> The DCE decodes this as a sequence of 3 + (<length>-1Fh).
<105off>
<105on> <42h>
<43h> Circuit 105 is OFF.
Circuit 105 is ON.
<singleEMp>
<doubleEMp> <58h>
<59h> The DCE decodes this as one <99h> in user data.
The DCE decodes this as <99h><99h> in user data.
<singleEM>
<doubleEM> <5Ch>
<5Dh> The DCE decodes this as on <19h> in user data.
The DCE decodes this as <19h><19h> in user data.
<poll> <5Eh> The DCE decodes this command and deliver a set of status commands,
one for each circuit enabled.
Supported V.80 DCE-to-DTE Commands
<extend0> <length>
<status> <rest of command> <60h>
<62h> The DCE decodes this as a sequence of 3 + (<length>-1Fh).
<106off>
<106on> <62h>
<63h> Circuit 106 is OFF.
Circuit 106 is ON.
<125off>
<125on> <6Ah>
<6Bh> Circuit 125 is OFF.
Circuit 125 is ON.
<singleEMp>
<doubleEMp> <76h>
<77h> The DCE encodes this as one <99h> in user data.
The DCE encodes this as <99h><99h> in user data.
<singleEM>
<doubleEM> <7Ch>
<7Dh> The DCE encodes this as on <19h> in user data.
The DCE encodes this as <19h><19h> in user data.