Specifications

Installation and Operation Manual Appendix C Operating Environment
FCD-E1LC Ver. 1.0 Ethernet Transmission Technology C-13
for the transmit and receive directions. Therefore, each node is capable of
simultaneously transmitting and receiving (full-duplex operation), thereby
doubling the effective data rate on the LAN.
Most Ethernet interfaces are capable of operation at the two basic rates,
10 Mbps and 100 Mbps (such interfaces are designated 10/100BaseT). Therefore,
four operating modes are possible.
These modes are listed below in ascending order of capabilities:
• Half-duplex operation at 10 Mbps.
• Full-duplex operation at 10 Mbps.
• Half-duplex operation at 100 Mbps.
• Full-duplex operation at 100 Mbps.
Autonegotiation
To ensure interoperability (which practically means to select the highest transport
capability supported by all the equipment connected to the LAN), two approaches
can be used: manual configuration of each equipment interface, or automatic
negotiation (auto-negotiation) in accordance with IEEE Standard 802.3.
The auto-negotiation procedure enables automatic selection of the operating
mode on a LAN, and also enables equipment connecting to an operating LAN to
automatically adopt the LAN operating mode (if it is capable of supporting that
mode).
When auto-negotiation is enabled on all the nodes attached (or trying to attach)
to a LAN, the process is always successful. However, even if the nodes on an
operating LAN are manually configured for operation in a fixed mode, a
late-comer node with auto-negotiation capability can still resolve the LAN
operating rate can be resolved, thereby enabling it to adopt the LAN rate. Under
these conditions, an auto-negotiating node cannot detect the operating mode
(half or full duplex), and therefore they will default to half-duplex. Therefore, as a
practical configuration rule, the full-duplex mode should not be enabled without
enabling auto-negotiation, except when all the nodes have been manually
configured for the desired operating mode (which may of course be full duplex).
The standard protocol that permits intelligent 10/100BaseT Ethernet ports to
automatically select the mode providing the highest possible traffic handling
capability also provides the following additional capabilities:
 Automatic detection and correction of MDI/MDIX crossover and polarity,
which enables connecting the FCD-E1LC Ethernet port to any other port
(station or hub) by any type of cable (straight or cross-wired)
 Use of 802.3 flow control in the full-duplex mode and backpressure flow
control in the half-duplex mode.