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AT commands: Detailed description
29
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devolo MicroLink ISDN i
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EN
*AT\Q3
: Bidirectional RTS/CTS handshake
AT\Q4
: Unidirectional XON/XOFF handshake
This command is used to select a variety of handshake procedures for serial
port data flow control.
Data flow control is especially important if the transmission speed to/from
the computer is not identical to the speed on the telephone side. This is the
case when using error correction and data compression, for example. With-
out a handshake procedure the danger of a buffer overflow is inevitable.
The data flow in the interface lines is monitored RTS (Request To Send) and
CTS (Clear To Send) when using a hardware handshake with the commands
AT\Q2
and
AT\Q3
. Data output to the computer is stopped if the RTS signal
line is OFF. The transition to ON permits the output of the received data to
continue. If the MicroLink ISDN i continues to receive from the telephone
line, the data is temporarily stored in the receive buffer. If the send buffer of
the MicroLink ISDN i is full, it switches the CTS (Clear To Send) signal line to
OFF, stopping the data output from the computer.
The commands
AT\Q1
and
AT\Q4
are used to select a software handshake
using the XON/XOFF characters. If the MicroLink ISDN i receives the <DC3>
character (S-s = XOFF) from the computer, then the data output is stopped
until a <DC1> (S-q = XON) is sent. Conversely, the MicroLink ISDN i sends a
<DC3> or <DC1> sequence to the computer if a transmission buffer is full or
ready again. Whether the XON and XOFF characters are sent to the MicroLink
ISDN i depends on the setting of the command
AT\X
. They are not sent by
default.
In unidirectional handshake processes, the handshake signals issued by the
computer are ignored.
S
Set and read the internal register
ATSn=x
: Sets register n to value x
ATSn?
: Reads the value of register n
ATSn
: Sets pointer to register n
AT?
: Reads the value of last register used
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