ZyXEL Communications ISDN Terminal Adapter Omni.Net Lite, User Manual

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Omni.Net Lite User’s Guide
Chapter 2 Using the Utility 36
2.6 RS-232 Port: V.24 Signal
The V.24 signal screen describes ways to treat data control signal for data transmitted via the
RS-232 serial interface of the TA. You can also use this screen to configure how to control
data flow between the computer and the TA.
2.6.1 RS-232 Flow Control
RS-232 Flow control is used to control data flow between devices, such as two modems or a
computer and a modem, using a serial connection. Standard flow control protocols include
hardware (RTS/CTS) flow control and software (XON/XOFF) flow control.
The RTS (Request To Send) and CTS (Clear to Send) lines of a RS-232 serial cable signal
flow control handshaking. In the following example,
A is a TA and B is a computer. For
upstream traffic from B to A , when device A ’s receive buffer is nearly full, it lowers the CTS
line (the CTS LED is off) to signal device B to stop sending data. When A is ready for new
incoming data, it raises the CTS signal (the CTS LED is on) to resume transmissiom. For
downstream traffic from A to B , B sets the RTS line to have A stop or restart sending data.
Figure 11 CTS/RTS Handshake
Flow control can also be done using the XON character (by pressing Ctrl-Q on the keyboard)
and XOFF characters (by pressing Ctrl-S) in a data stream. When a device receives an XOFF
signal from another device, it suspends or stops data transmitting to that device until receiving
an XON (Ctrl-Q) signal from the same device. An XOFF character is sent when the receive
buffer is nearly full. An XON signal is sent when the buffer is no longer full. Binary files may
contain these signal characters and cannot be sent with XON/XOFF flow control protocol.
Threshold of data
loading to ADD/DROP
one channel
This field is not available if you select Enable Fixed MP .
Set the maximum threshold in the ADD field and the minimum threshold in the
DROP field. The TA adds the second B-channel when traffic is above the
threshold and drops the second B-channel when traffic is below the threshold.
Persist time for
monitoring threshold to
add or drop one
channel
This field is not available if you select Enable Fixed MP .
Set the time interval between calculating traffic load. The unit of a value is 5
seconds.
Table 6 RS-232 Port: PPP/MP Parameters
LABEL DESCRIPTION