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Chapter 4 – Serial Interface Control
The AT Commands described in this chapter allow the external application to determine various settings related to
the Multi-Tech wireless modem's serial interface.
4.1 AT\Q Flow Control
Exec Command Syntax:
Response:
Parameter Description:
<n>
0
Disable flow control. Default.
1
XON/XOFF software flow control
2
Only CTS by DCE (TA)
3
RTS/CTS hardware flow control
Recommended for the following procedures: incoming or outgoing data calls, and MUX mode.
Notes:
•
When using XON/XOFF flow control (AT\Q1) in online mode, +++ should not be used while the data transmission
is paused with XOFF. Before entering the command mode with +++ the paused transmission should be resumed
using the XON character.
•
With AT+IFC, flow control can be set separately for each data direction, while AT\Q applies to both directions.
The two commands influence each other, i.e. settings made with AT\Q apply to AT+IFC and, vice versa, AT+IFC
changes the AT\Q setting.
4.2 AT&C Set Data Carrier Detect (DCD) Mode
Description:
Exec Command Syntax:
Response:
Parameter Description:
<value>
0
DCD line is always ON.
1
DCD line is ON in the presence of data carrier only. Default.
2
DCD line shall be on when one or more Internet services defined on the related serial channel are in state
"Connecting" or "Up" as described below. For details on the various service states refer to AT^SISI,
parameter <srvState> or AT^SISO, parameter <srvState>.
•
SOCKET, HTTP, SMTP, POP3: DCD shall be on when <srvState>="Connecting" or "Up"
•
FTP: DCD shall be on when data channel is connected; i.e., <srvState>="Up"
4.3 AT&D Set Data Terminal Ready (DTR) Line Mode
Description:
Exec Command Syntax:
Response:
Parameter Description:
<value>
0
ME ignores status of DTR.
1
ON->OFF on DTR: Change to command mode while retaining the connected call.
2
ON->OFF on DTR: Disconnect data call, change to command mode. During state DTR = OFF auto-answer
is disabled. Default.
Multi-Tech Systems, Inc. AT Commands for EDGE Modems (S000371G)
Commands
AT\Q[<n>]
OK
If RTS/CTS flow control is not supported by interface and <n> is 2 or 3:
ERROR
The AT&C command determines how the state of the DCD line (circuit 109) reflects EDGE
modem's internal activity.
AT&C[value]
OK
AT&D determines how the ME responds if the DTR line is changed from ON to OFF
during data mode.
AT&D[<value>]
OK
Chapter 4 – Serial Interface Control Commands
57
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