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Appendix A
1
RS-422 Output Format for non-Campbell Datalogger
Applications
This output operates at 9600 BAUD (One Start Bit, 8 Data Bits,
No Parity, One Stop Bit). A 24-byte string is sent once per
second. See section 10.2 for string definition.
A two-line output provides a bi-directional serial port, running at
9600 BAUD (8-bits, one Start Bit, One Stop Bit, no parity), to
allow communication with aircraft electronics and external test
equipment.
2
Built In Test (BIT)
Built-In-Test (BIT) capabilities of the freezing rain sensor consist
of hardware, continuous, power-up, and operator-initiated tests.
Whenever a failure is detected and verified, the freezing rain
sensor stops detecting and annunciating icing conditions and the
heaters are disabled. Failures detected in Initiated and Continuous
BIT are counted and enunciated once they have been verified. To
eliminate nuisance errors, failures are verified by delaying
(debouncing) the failure for a period of time. Failures detected in
Initiated BIT are latched and power must be cycled on and off to
remove a failure. If failures detected in Continuous BIT go away,
the ice detector changes back to normal mode, and once again
enables all ice detection functions.
3
Hardware Built-In-Test (BIT)
Hardware BIT is comprised of a watchdog timer that forces the
microcontroller to re-initialize if it does not receive a strobe every
1.6 seconds. An internal voltage monitor forces the
microcontroller to the reset state if the internal 5VDC power
supply falls below 4.65 VDC and holds it there until the power
supply returns above 4.65 VDC. When the microcontroller is
reset, no output string is sent.
4
Continuous Built-In-Test (BIT)
12