Bay Networks 3395A, Configuration Manual

Page: 140 / 146

Modem and Flow Control Operation
A-10 893-826-A
Hardware Flow Control
Units with 6-wire interfaces support hardware flow control using the DTR and
DCD signal lines of a serial port. Using the DTR and DCD signal lines for
hardware flow control, however, precludes their use as modem control signal
lines.
Units with 8-wire interfaces support hardware flow control using the RTS and
CTS signal lines. These units support the concurrent use of hardware flow
control and modem control.
When using hardware flow control, XON and XOFF characters can be treated
as normal data, and hardware flow control is useful whenever XON or XOFF
characters need to be interpreted as data. Hardware flow control is not
implemented in all devices that can be attached to the port.
Setup
The following PORT characteristics affect the flow control capability:
• FLOW CONTROL
• INPUT FLOW CONTROL
• OUTPUT FLOW CONTROL
• SESSION
• TYPEAHEAD SIZE
The DEFINE/SET PORT FLOW CONTROL characteristic defines the default
flow control mode of operation for the server port. The possible modes of
operation are:
• CTS—Hardware flow control
• DISABLED—No flow control
• DSR—Hardware flow control
• ENABLED—XON/XOFF flow control
• XON—XON/XOFF flow control
Although there are five choices for 6-wire interfaces, this characteristic
effectively takes on one of three values:
• No flow control
• Software flow control using XON/XOFF
• Hardware flow control (the PORT FLOW CONTROL keywords CTS and
DSR are synonymous)
For 8-wire interfaces, there are separate CTS/RTS and DSR/DCD hardware
flow control options, but only one of them can be used at a time.
Nonprivileged users and users at privileged ports can select among these flow
control modes using a SET PORT or DEFINE PORT command.