Contemporary Research TD960801-0MC - Manual (Page 29)

TD960801-0MC
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MAC ID tests as in the case of DeviceNet. However, if a
remote bridge loses power while all other devices remain
powered, the failure mode should be no different than cutting the
cable in the middle of a CAN segment. When power is restored
to the remote bridges, the restart sequence should be the same as
if the maintenance person reconnected a disconnected cable.
CAN networks are usually configured in a bus or multidrop
topology while ARCNET can be configured as a bus, star or
distributed star topology. Therefore CAN implementations can
take advantage of the more flexible ARCNET cabling options.
Do not cascade EXTEND-A-BUSes beyond two since the delay
stackup could be excessive. Instead connect all EXTEND-A-
BUSes in a star topology using a hub thereby reducing data
latency to that of two EXTEND-A-BUSes.
Implementing fiber optics over any reasonable distance with
CAN is difficult due to the increased delays caused by the
additional circuitry. However, fiber optic ARCNET solutions
are readily available. Therefore, the benefits of fiber optics can
be gained simply by adding remote bridges. Note that the
propagation delay of fiber optic cable (5 ns/m) is 25% more
than that of coaxial cable. This is important when calculating
ARCNET delay margin and was considered when setting the 4.8
km fiber optic limit.
3.4 LED Indicators
One CAN Status LED and one LINK Status LED are provided
in order to convey information regarding their respective ports.
When LEDs flash, they will flash approximately at a rate of 0.5
seconds on and 0.5 seconds off.
3.4.1 CAN Status LED
A dual color LED (red/green) is used to identify status of the
CAN port. After a power-on sequence, the LED indications are
as follows: