6100 MPS-B Programming Manual

6100 MPS-B LINK MANAGEMENT
Modem Signals
DTR For switched lines, you control the raising and dropping of
DTR through CONTROL Connect or Disconnect requests (see
Section 3).
For leased lines, DTR is raised after the line has been
configured and when the first READ or WRITE request is
processed. DTR remains up until the line is stopped, or
until you issue a CONTROL Disconnect request from your
application process.
DSR 6100 MPS-B tracks the state of DSR. DSR must remain up
throughout the duration of the connection. Whenever DSR is
not present, or if it drops after request initiation, READ
or WRITE requests are aborted with status = 140 (modem
error). Should it drop, DTR also drops and the current, or
next, request is completed with a modem error status
condition. Requests are not retried when DSR drops.
RTS For half-duplex lines, RTS is raised before, and dropped
after each transmission on the line.
For full-duplex lines, RTS is raised and remains up for the
duration of the connection.
CTS The state of CTS is monitored only when 6100 MPS-B
transmits (writes) data on the line. The module always
waits for CTS to be raised before beginning to transmit.
If CTS does not raise, a timeout error occurs--the
application request terminates. If CTS drops during the
transmission, A CTS error is reported to the application
process. An OFF to ON state transition is not required;
CTS simply needs to be up when 6100 MPS-B is transmitting
data.
DCD The state of DCD is monitored. A few DCD ON/OFF state
transitions are permitted (DCD fluttering) with no harmful
result. If DCD should drop during a read operation, 6100
MPS-B takes no notice.
For a write operation, both the MPSBCONTROLCF and the
MPSBNOCONTROLCF configuration parameters determine when to
transmit data. If Control CF is set ON (MPSBCONTROLCF),
transmission occurs (the line is turned around) after DCD
drops. If Control CF is set OFF (MPSBNOCONTROLCF),
transmission occurs without regard for the carrier state.
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