ARINC629 Flashcards
What is the maximum amount of Rx/Tx the 629 bus will allow?
120 Tx/Rx
What type of serial data bus is the ARINC629?
Bi-directional/Duplex
What type of wires can the ARINC629 be and how long are they?
Can be 100m twister copper
Unlimited length fiber optic
What is the speed of the ARINC629?
2MB/s
What is the improvement of ARINC629 from 429?
Less weight and high speeds
Can you transmit on more than one LRU at a time for the ARINC629?
No, can transmit only one at a time
How many bus control units does the ARINC629 have?
It does not have any bus control units
How many data busses do you need for 2 way communications?
Only one data bus for 2 way communication
What type of coupling does the ARINC629 use and what are its advantages?
No physical interruption
less loose connections
improved reliability
What is the initial data produced by the LRU and in what format?
A digital signal in the Manchester format
When the doublet changes from a binary 1 to 0 and vice versa, what does it produce?
It produces a short pulse(bumps)
How does the clock pulse react on the 629 and what is its purpose?
Becomes opposite of the current binary high/low and is for synching
Why is the Receiver voltage lower than the transmit voltage?
For system losses
What are the benefits of using fiber optic cable?
immune to EMI and lighting transients
What is the copper wire impedance?
130ohms
What is the purpose of the timing signal in each bit?
Self clocking
How long is each bit?
100uS
This component moves data to and from the LRU memory, what is it?
Terminal Controller
What is the purpose of the serial interface module?
- Connects TC to data bus STUB
- Changes Manchester current to analog voltage doublet
- informs TC of system failure
How many wires/cables does the stub have?
4 (2Rx, 2Tx)
What is the max length of the stub?
75ft
What is the purpose of the stub cable?
Connects TC to CMC
What is the CMC and what is its purpose?
It is the current mode coupler and its to get the LRU to the 629 bus using a transformer coupler
How many inductive couplers in one unit and what is the purpose?
2 inductive couplers in one unit
one for redundancy
In transmit, the CMC does what?
Changes v doublet to current doublet
Current doublet to V doublet is changed where?
Receiver CMC
Each message has what?
31 word strings
4bit sync gap ident
How many data words in 1 word string?
256 data words
starts with label then data words
The Label word has how many bits and what are they?
20bits
- 12 label
- 1 parity
- 4 label extension
- 3 sync pulse
The Data word has how many bits and what are they?
20 bits
- 16 data
- 1 parity
- 3 sync
What is the purpose of the PPSSP and PSSP?
Syncing at beginning of each word
The 629 bus is also referred to as?
Periodic, Aperiodic multi-tx bus
What are the 3 timing signals used to sequence the transmission of the 629?
Terminal Gap
Synch Gap
Transmit Interval
Which is longer than the longest TG?
Synch Gap
What is the purpose of the TG?
determines the priority of transmission for LRUs
What does a short TG mean?
High priority
What is the purpose of the Synch Gap?
acts as a reset signal
- LRU can only tx once until next SG
What is the purpose of the TI?
prevents any one user from dominating the bus
What is a periodic bus?
All tx completed within TI completion
If the TI is exceeded due to an LRU tx longer than average message, what is the mode now?
Aperiodic
What does an impedance change signify?
A faulty bus
If you pass the ohmeter test but still fail to transmit the signal what is the issue?
High impedance
What are the 3 ways transmission of digital data can be affected by the data bus system?
Drop Outs
Attenuation
Interference
When a portion or portions of the signal are lost during tx what is it being affected by?
Drop Outs
What is Drop Outs caused by?
Loose Connections
Intermittent Signals
What does attenuation do?
makes signal weak or tx V too low that receiver does not recognize
How does attenuation happen?
Loss of power due to resistance, dbm, db
How do you solve attenuation?
LRU isolation
LRU inductive coupling
What is it called when unwanted signals are induced into the bus?
Interference
What causes interference?
Improper shielding
Leaks
