Multi-Tech Systems ISIHP-2U - Manual (Page 91)

MultiModemISI Hybrid Series, ISIHP-2S/2U/4S/4U/4SD 91
Modem AT Commands & S-Registers
&K4 enables XON/XOFF software flow control. XON/XOFF flow control
is an in-band method of data flow regulation. In-band data regulation means
that the XON (^Q) and XOFF (^S) characters are inserted into the stream of
data rather than using separate control lines. When an XOFF character is
detected, the data stream is suspended until an XON character is detected. If
you issue the &K4 command to the modem, it will respond to XON/XOFF
pacing, and use XON/XOFF characters as its own method of flow control to
the computer. (This is the same as \Q1.)
The drawback to using this method of pacing is that some files may contain
these characters as part of the file data. If such a file is transferred using a
modem with XON/XOFF flow control enabled, the file transfer could fail
due to indefinite suspension.
\Qn Local Flow Control Selection
n = 0, 1, or 3
Default: \Q3
Allows you disable flow control and enable hardware or software flow
control.
\Q0 completely disables data flow control initiated by the modem. (This is
the same as &K0.)
\Q1 enables XON/XOFF software flow control. XON/XOFF flow control is
an in-band method of data flow regulation. In-band data regulation means
that the XON (^Q) and XOFF (^S) characters are inserted into the stream of
data rather than using separate control lines. When an XOFF character is
detected, the data stream is suspended until an XON character is detected. If
you issue the &K4 command to the modem, it will respond to XON/XOFF
pacing, and use XON/XOFF characters as its own method of flow control to
the computer. (This is the same as &K4.)
The drawback to using this method of pacing is that some files may contain
these characters as part of the file data. If such a file is transferred using a
modem with XON/XOFF flow control enabled, the file transfer could fail
due to indefinite suspension.
\Q3 enables modem’s use of Clear to Send (CTS) signal on the RS-232/
V.24 interface to regulate data flow. When CTS drops, data flow is
suspended until the signal goes high (on) again. This method of flow control
works in conjunction with pacing (i.e., computer-initiated flow control),