Multi-Tech Systems ISIHP-2U - Manual (Page 119)

MultiModemISI Hybrid Series, ISIHP-2S/2U/4S/4U/4SD 119
Terminal Adapter AT Commands & S-Registers
Selects method by which the TA controls the flow of data to and from the
computer, to prevent either device from accepting data faster than it can
handle. The TA provides flow control in both directions. When the TA halts
data flow, it is called flow control; when the computer halts data flow, it is
called pacing.
&E3 Disable flow control by the TA.
&E4 Hardware flow control. &E4 causes the TA
to use the CTS signal to regulate flow
control. When CTS goes low, data flow
from the computer is suspended until CTS
goes high again. This method works with
pacing, which uses the RTS signal on pin 4.
Hardware flow control cannot be enabled
unless an error correction protocol is
selected.
&E5 XON/XOFF flow control. This is an in-band
method, where the XON and XOFF
characters (^Q and ^S, respectively) are
inserted into the data stream, rather than
using separate control lines. When an XOFF
character is detected, the data stream is
suspended until an XON character is
detected. The drawback to this method is
that some files may contain these characters,
causing the file transfer to be suspended
indefinitely.
&E6 When XON/XOFF pacing is active, the TA
responds to and discards the XON/XOFF
characters from the computer.
&E7 When XON/XOFF pacing is active, the TA
responds to the XON/XOFF characters and
passes them through the communications
link to the remote device, thereby pacing the
remote terminal adapter as well.
&E12 Disables pacing
&E13 Enables pacing.