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11 Time of Validity Output (TOV)
11.1 TOV Summary
The 1775 IMU provides an optional RS-422 differential output on the external connector
(named TOV-OUT+/TOV-OUT-) to indicate the time at which the data being output on the
serial port can be considered to be relevant. This output is only relevant when the unit is in
Normal Mode (i.e., unit is set to output binary data on the serial port). When the unit is not in
Normal Mode (e.g., it is in Configuration Mode) the TOV indication should be ignored.
When used, KVH recommends that this signal be connected to a properly terminated RS-422
receiver to prevent signal reflections and crosstalk. If not used, it may be left unconnected.
The TOV signal can be used as an indication that output of a data message is going to occur.
It can also be used by a system to timestamp the subsequent data message as it will be very
close in time to the IMU’s sampling of its rotational and linear sensors (refer to Table 11-1).
The behavior of the TOV signal depends on whether the unit is generating its own (internal)
timing (default or =MSYNC,IMU) or if it is relying upon the user-driven timing associated with
the Master Synchronization Input (see Section 11.3 for details).
11.2 TOV Timing
TOV is shown in the diagram as a single signal and assumes that TOV+ and TOV- operate
together as a differential pair to define the active (high) or deasserted (low) state.
Figure 11-1: TOV Output Timing Relative to Serial port Activity
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