190302 dB Flashcards
What is loop or ring topology?
Early networks used a loop or ring topology in which all modules are wired in series.
One major disadvantage of the loop topology is that if one module on the bus loses power or ground the whole network could lose communication
What is star topology?
In the star topology master module controls the data bus and the remaining modules are dependent on slave modules
This configuration allows the network to continue to communicate even when power or ground is lost to a module
What is linear topology?
Linear topology in which there is a main backbone with stops running to each module there is no master module all modules receive all broadcast would speed up the rate of data communication
What is MID?
Message identifier
- is one byte long and indicates the source address of the transmitting node
What is PID?
Parameter identifier
- is usually one bite long and indicates to what parameter the following data correspondence
What must follow a PID?
All PIDs must be followed by at least one data value. The length varies depending on the amount of data transmitted but cannot exceed 18 bites
What is “topology”?
Topology describes a logic structure of the control modules on the data bus
The checksum comes before the final byte of data T/F?
False, it comes after the final byte of data
What is one of the first tests you need to conduct with all multiplexed systems?
Determine if the system is receiving power.
When testing multiplexed systems, we can use any multi meter. T/F
False; Failure to use a high impedance meter will result in damage to the electronic components.
SAE J1939-11 multiplexed systems run at what speeds?
250 kb/s
Difference between shielded and unsheilded j1939 is?
Shielded twisted pair has a drain wire
Terminating resisters are used at each end to prevent?
Standing waves
Signal corruption occurs when?
An electromagnetic force is induced in the data link. Example. Run across a data link , twisted pair looses integrity or anything with any magnetic properties
Which of the following best describes multiplexing?
a) the ability to communicate analog signals between communication devices
b) the ability to send and receive digital electronic signals over a pair of wires
c) the ability to increase the amount of wires necessary to connect inputs and
outputs
d) the ability to control devices wirelessly
the ability to send and receive digital electronic signals over a pair of wires
How does multiplexing reduce the number of conductors used on heavy equipment?
by allowing control modules to share data for inputs
Which of the following is the measurement of data transfer speed over a network?
a) protocol
b) baud rate
c) data link
d) backbone
baud rate
What is the baud rate of J1939?
250 kb/s
Which of the following is the communication language used between control modules? a) protocol b) baud rate c) data link d) back bone
protocol
How do you reduce interference of data communication?
by using twisted wire pairs and drain wire shielding
Which topology is typical for most modern mobile equipment units?
linear
Explain serial communication over the CAN network.
In serial communication one bit is broadcasted after another in sequential order. Each
controller contains a CAN transceiver (transmitter/receiver) chip that is designed to
follow the CAN protocol. There is no master control device in a CAN network: each
module knows which messages and modules have priority and must wait until the
data bus is idle to start a broadcast.
Which of the following terminates and validates the message communicated over a J1587/J1708 data link? a) message identifier (MID) b) parameter identifier (PID) c) parameter data bytes d) checksum
checksum
What is the color code for a J1587/J1708 twisted wire pair?
orange and white
Which of the following replaces the parameter identifier (PID) in a J1939 message?
a) parameter group number (PGN)
b) suspect parameter number (SPN)
c) failure mode identifier (FMI)
d) arbitration field
suspect parameter number (SPN)
Which of the following best describes the construction of the J1939-11 heavy cable?
a) unshielded twisted pair
b) shielded twisted pair
c) unshielded twisted quad
d) shielded twisted quad
shielded twisted pair
What is the drain wire connected to in a shielded twisted pair?
battery ground
Identify and explain the two (2) reasons why data links are twisted.
a) The twist helps provide immunity to magnetic fields. A changing magnetic field causes voltage (noise) to be induced into both conductors. b) The twist helps maintain constant capacitance of conductors
What is the purpose of the terminating resistors?
To minimize the occurrence of standing waves
When performing the CAN data wire test, which of the following is the expected
reading of a properly functioning system?
1 MΩ – 4 MΩ
When performing the terminating resistor test on a J1939 data link, what does a
reading of less than 60 Ω indicate?
short
Which of the following best describes the construction of the ISO11783 cable?
a) unshielded twisted pair
b) shielded twisted pair
c) unshielded twisted quad
d) shielded twisted quad
unshielded twisted quad
Explain the two functions the terminating bias circuit performs on the ISO11783 data
link
The terminating bias circuit uses dedicated battery power and ground supply along
with the CAN-High and CAN-Low signal to provide electrical bias and termination
to the network, preventing reflections from occurring in the system that would create
interference.
Which of the following best describes the function of the ISO11783 tractor
breakaway connector?
a) to allow machine manufacturers to have their machines connect to their
implements only
b) to allow any machine to connect to any implement
c) to allow machine manufacturers proprietary access to implements
d) to decrease the versatility of machine and implement combinations
to allow any machine to connect to any implement
CAN-high and CAN-low voltages can be checked how?
They can be measured between their pin and he battery ground.
What is one way to tell if you are using J1939?
The J1939 has 9 pins.
