Date: 2022-09-26 Page 29 of 48
Operation and Installation CD401MR-SC
All parameters within each NMEA sentences are checked for checksum, legal range,
validity and timeout.
Bad checksum ( - - - - -)
If the checksum eld (*hh) is present, the value is checked. The screen will indicate bad
checksum by displaying minus signs instead of the value (- - - - -). If no checksum eld
is present, no checking is performed.
Illegal range and validity (. . . . .)
Some values must be within a range. If a value is out of range, the following exception
is performed:
• Wrap around: The displayed value will start from zero again after reaching
the maximum/minimum value (trip values, only).
• Limited value: The maximum or minimum value will be displayed (speed and
temperature values).
• Illegal value: The value has no meaning (ex. heading values above 360
O
). The
screen will indicate illegal value by displaying dots instead of the value (. . . .).
A Null eld is a eld in the NMEA sentence without any character between two delimiter
characters. A Null eld indicates that the value is unreliable or not available. The screen
will indicate a Null eld by displaying dots instead of the value (. . . . . ) if no value is
received within the timeout timeframe.
Some parameters has a status parameters associated with them (A = data valid, V = data
invalid). The screen will indicate an invalid parameter by displaying dots instead of the
value (. . . . .) if no new valid value is received within the timeout timeframe.
Timeout (ERROR)
The timeout value for each parameter within each NMEA sentence is 10 seconds. The
screen will indicate timeout by displaying an error message (ERROR) if no new value
is received within the timeout timeframe.
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