ETTC'2003 - SEE

establishing different socket connections, the Ethernet interface can be used for
a number of different functions simultaneously. Figure 3 illustrates the various
uses of the Ethernet interface in the telemetry recording workstation.
Ethernet (10/100 BaseT)
1. File Transfer Protocol (FTP)
2. Command socket
3. Digital data socket
4. Peer-to-peer socket
Figure 3. Use of the Ethernet interface
One of the primary uses of Ethernet is for transferring recorder configurations to
and from a host workstation. Using the TCP/IP and FTP protocols, setup files
can be quickly transferred to the telemetry recorder prior to a mission. Using this
method, a library of configurations can be stored and used when necessary.
Another benefit is the reduction of costly set-up time.
Another important use of Ethernet is for command and control of the telemetry
recorder. Flight test recorders have traditionally utilized RS232 or IEEE-488 for
host control. Ethernet is a more efficient and cost-effective interface to
implement. By opening a command socket, host control commands can be sent
to the system. Typical commands include system status query, start and stop
recording, recording speed and editing text information.
Ethernet can also be used to send digitized data to the telemetry workstation.
Because this interface does not have the raw bandwidth or determinism of other
digital interfaces, a new approach was designed for real-time digital data transfer.
The traditional approach to sending digitized waveforms is to have the host
stream data points for each channel in real-time or close to real-time. Data rates
and resultant loads on both host and recorder can be high. The alternative
method is to send line segments based on the minimum and maximum waveform
values for a delta T. The value of delta T depends on chart speed. The signal
sample rates are set by the host in order to maintain the required bandwidth.
The impact of transmission delays is minimal because the line segments are built
in the host using a fixed time period that the telemetry recording workstation also
uses to control the rate of printing and display. The data set containing the line