Applications - CAN System Engineering - page 273

Table 5.3 Smoke detector data field
Data byte MSB LSB Description Format

1 7 5 Spare/not used -

4 4 Detector Warning Discrete

3 3 Prefault threshold exceeded Discrete

2 2 Detector standby Discrete

1 1 Detector alarm Discrete

0 0 Detector failure Discrete

2 7 0 Trouble shooting data Binary

3 7 2 Spare/not used -

1 0 MSB contamination level Binary

4 7 0 LSB contamination level Binary

5 7 2 Spare/not used -

1 0 MSB smoke level Binary

6 7 0 LSB smoke level Binary

7 7 2 Spare/not used -

1 0 MSB temperature Binary

8 7 0 LSB temperature Binary

Table 5.4 Meaning of the status bits
Designation bit Meaning

Failure 0 The smoke detector is no longer able to detect smoke or to

communicate this information in a reliable manner

Alarm 1 Smoke is detected and confirmed

Standby 2 The smoke detector is able to detect smoke and communicate

this information in a reliable manner

Prefault 3 The smoke detector optical cell contamination level

has exceeded the internal threshold for triggering a
corresponding maintenance message

Warning 4 The CAN TX error counter has exceeded 96

classified as catastrophic. A catastrophic event is defined as an occurrence leading
to total loss of the aircraft and occupants and must be ruled out with a defined level
of probability of failure < 1 × 10 −9 . Therefore, various network management mecha-
nisms are necessary to ensure proper system configuration during initialization and
normal operation.

5.3.4.5 Power-Up Configuration Control

The normal expected configuration of smoke detectors is fixed in a lookup table
within the network master's operational software. At power up or system initializa-
tion, the current configuration is compared with the expected through a mechanism
called Configuration Check Request. During the Configuration Check Request pro-
cess, the network master broadcasts the Configuration Check Request as an R_PDO