Lowspeed Flashcards
(24 cards)
What is the job of the bus controller?
To control everything that happens on the bus. It initiates all data transfers, it must Tx, Rx and coordinate the transfer of information.
What is the low speed databus called?
Stanag 3838 which is the NATO standard
MIL-STD-1553B US AIRFORCE
What is a remote terminal?
It is an electronic interface between the LRI and the Databus like a doorway.
How often does a major cycle last?
640 mS
What is a bus monitor?
It allows for connection of the DBTE
What’s the Stanag 3838 cable used?
Two conductor, twisted, screened, overall insulated cable
What is the minimum number of twists per foot for the cable?
4
What are the benefits of this cable?
Reduction in common mode noise
Impedance 70ohms
Cable attenuation shall not exceed 1.5db/ft
What type of stubs are used?
Transformer couplings
What’s are the characteristics/advantages of transformer couples?
Stub length coupling up to 20ft Electrical isolation Impedance matching Common mode noise reduction Maintains wave integrity
How is a command work made up?
3 bits sync 5 bits terminal address 1 bit Tx/Rx 5 bits sub address/mode 5 bits data word/mode code 1 bit parity
What is the structure of a data word?
3 bits sync
16 bits data
1 bit parity
What is the structure of a status word?
3 bits sync 5 bits remote terminal address 1 bit message error 1 bit instrumentation 1 bit service request 3 bits reserved 1 bit broadcast command 1 bit busy 1 bit subsystem flag 1 bit dynamic bus control 1 bit terminal flag 1 bit parity
What are the Stanag transaction protocols?
BC - RT RT - BC RT - RT Mode command without data Mode command with data Tx Mode command with data Rx
BC - RT’s
RT - RT’s
Mode command without data
Mode command with data Rx
How many minor cycle are there for every major and how often are they?
32 or 20 mS
Explain a BC - RT transaction
BC send command word and data word to RT
Message response time gap 4-12micro Seconds
RT responded with status word to BC
Explain a RT - BC transaction
BC send a command word to RT to Rx
Message response time gap
RT sends stays word and data word to BC
Inter-message gap of at least 4microS
Describe an RT - RT transaction
BC sends command word to Rx RT
BC send command word to Tx RT
Message response time gap
Tx RT send status word and data word Rx RT
Message response time gap
Rx RT send status word to BC
Describe a BC - RT’s broadcast
BC sends command word and data word to RT’s
Explain an RT - RT broadcast
BC sends command word to Rx RT’s
BC send command word to Rx RT
Message response time gap
Tx RT sends status word to BC
Explain the three levels of validity
Bit validation
Word validation
Message validation
Explain bit validation
There is valid Manchester bi code
Explain message validation
Contiguous (at least 4 microS parity to sync)
Word count
Explain word validation
Valid sync field (bits1,2,3)
Info field has 16 bits
Word parity (odd)
