Comtrol DeviceMaster NS-Link - Manual (Page 39)

DeviceMaster Driver User Guide: 2000595 Rev. A Configuring Device Properties - 39
NS-Link Device Driver Configuration
Device General Tab Description
Device Name
This is the default name assigned by the driver and it cannot be
changed. You can use the User-Friendly Device Name field to provide
custom device names for your installation.
User-Friendly Device Name
Use this field to enter a more descriptive name. The name that you
assign is not saved until you click Apply or OK.
Keep Alive Timeout (seconds)
Default = 120 seconds
Use this option to set the amount of time in seconds that this
DeviceMaster waits until it closed this connection and frees all the
ports associated with it. The Keep Alive feature works in the
following way.
During normal operation the driver periodically sends a connection
check to the DeviceMaster, and the DeviceMaster then returns a
response. There are two timers: one in the driver, and one in the
DeviceMaster. These timers are reset when a connection check
signal is received. If a connection is broken, that is, a check is not
received, the data is stored in the computer and/or the
DeviceMaster. Depending on the amount of time that has expired
since the connection was lost, the following happens:
• When the computer loses its connection to the DeviceMaster but
re-establishes it before the time-out period expires, any data
transmitted during this period is queued and sent when the
connection resumes.
• When the computer loses its connection to the DeviceMaster
and does not re-establish it before the time-out period expires;
the driver then purges any pending I/O data for ports on that
connection and returns all pending, and future I/O commands,
with the exception of the Close command, to the application with
an error indicating the disconnected status.
This is similar to the processing which occurs when the
computer receives a notification from the DeviceMaster that a
port release request was processed on a port it owns with the
exception that a different status is returned. When the
connection is re-established, the computer will attempt to re-
acquire the ports that were open when the connection was lost.
If the attempt is successful, normal operations resume for the
port. If any port fails to be acquired, then the computer will
continue to fail all further I/O operations, with the exception of a
Close request. When the Close request is received, the port can
then be re-opened.
• If the computer loses its connection and the time period expires,
the DeviceMaster places the port into a state that another
computer can establish a connection, locking out the original
driver when a connection is made. The driver will respond to all
I/O commands, with the exception of the Close command, with
an error indicating the disconnected status. If the port is still
available when the driver re-establishes a connection, then it
will claim the port and allow I/O to resume.