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ROC800-Series Instruction Manual
5-8
Communications
Revised Jul-14
mechanism is based on Carrier Sense Multiple Access with Collision
Detection (CSMA/CD). If two stations begin to transmit a packet at the
same instant, the stations stop transmitting (Collision Detection).
Transmission is rescheduled at a random time interval to avoid the
collision.
You can link Ethernet networks together to form extended networks
using bridges and routers.
Table 5-5. Ethernet Signal LEDs
Series 1 CPU
Signal
Function
RX
Lit when currently receiving.
TX
Lit when currently transmitting.
COL
Lit when Ethernet Packet Collision detected.
LNK
Lit when Ethernet has linked.
Series 2 CPU
Signal
Function
COL
Lit when Ethernet Packet Collision detected.
ACT
Blinks when activity (TX, RX, or LNK) occurs.
Use a rugged industrial temperature HUB when connecting Ethernet
wiring in an environment that requires it.
The IEEE 802.3 10BASE-T standard requires that 10BASE-T
transceivers be able to transmit over a link using voice grade twisted-
pair telephone wiring that meets EIA/TIA Category four wire
specifications. Generally, links up to 100 meters (328 feet) long can be
achieved for unshielded twisted-pair cable.
For each connector or patch panel in the link, subtract 12 meters (39.4
feet) from the 100-meter limit. This allows for links of up to 88 meters
(288 feet) using standard 24 AWG UTP (Unshielded Twisted-Pair) wire
and two patch panels within the link. Higher quality, low attenuation
cables may be required when using links greater than 88 meters.
The maximum insertion loss allowed for a 10BASE-T link is 11.5 dB at
all frequencies between 5.0 and 10.0 MHz. This includes the attenuation
of the cables, connectors, patch panels, and reflection losses due to
impedance mismatches to the link segment.
Intersymbol interference and reflections can cause jitter in the bit cell
timing, resulting in data errors. A 10BASE-T link must not generate
more than 5.0 nanoseconds of jitter. If your cable meets the impedance
requirements for a 10BASE-T link, jitter should not be a concern.
The maximum propagation delay of a 10BASE-T link segment must not
exceed 1000 nanoseconds.
Signal coupling between the different cable pairs contained within a
multi-pair cable bundle causes “crosstalk.” 10BASE-T transceivers are