Specifications

Chapter 1 Introduction Installation and Operation Manual
1-12 Functional Description FCD-E1LC Ver. 1.0
Ethernet Port Interface Characteristics
The Ethernet port 10/100Base-T LAN interface supports auto-negotiation.
However, the user can also disable auto-negotiation and specify directly the
operating rate (10 or 100 Mbps) and operating mode (half-duplex or full-duplex).
The auto-negotiation process uses a standard protocol that permits intelligent
10/100BaseT Ethernet ports to automatically select the mode providing the
highest possible traffic handling capability. Therefore, when auto-negotiation is
enabled, the Ethernet port automatically selects the appropriate operating mode
as soon as it is connected to a LAN or to another Ethernet port.
The following additional capabilities are also available:
• 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.
The timing mode of the Ethernet channel interface is always DCE (that is, within
the FCD-E1LC the timing of the receive and transmit Ethernet channel paths is
always locked to the FCD-E1LC system clock).
Ethernet Switch Description
The FCD-E1LC includes an Ethernet switch with VLAN support that fully complies
with the IEEE 802.3/Ethernet V.2 standards, has user-selectable forwarding
algorithms, and provides extensive support for QoS features.
The Ethernet switch has two ports:
• An external port connected to the Ethernet (LAN) interface of the FCD-E1LC,
supported by a MAC controller that performs all the functions required by the
IEEE 802.3 protocol.
• An internal port connected to the main link interface of the FCD-E1LC, which
can be assigned timeslots in accordance with the desired throughput. This
port supports the HDLC protocol.
The frames passed by the MAC controller are transferred to an internal queue
controller, which controls the frame egress priorities and inserts them in two
separate queues.
Flow Control Options
The user can enable flow control. Flow control is available in both the half-duplex
and full-duplex modes:
• In the half-duplex mode, flow control uses a collision-based scheme to
throttle the connected stations when the free buffer space of the FCD-E1LC
Ethernet port is too low, to avoid discarding frames during congestion (this
approach is called
back pressure ). When the buffer space of the port is
almost full, its MAC controller forces a collision in the input port when an
incoming frame is sensed (the alternative, without flow control, is to discard
the incoming frame).