Contemporary Control Systems EISC Configurable Switches User Manual - Manual (Page 17)

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6
Plug-and-Play Operation
6.1
LED Indicators
P Power
S Fault Relay Status
#s Link/Activity
This LED glows green when power is
supplied to the EISC.
This LED glows green by default, but has no
function in Plug-and-Play mode.
Each port has one of these LEDs. If a link is
established, it glows green for 100 Mbps
operation or yellow for 10 Mbps operation. It
flashes as data transfer occurs. Even LEDs
are on the right; odd LEDs are on the left.
Figure 10 — LEDs
6.2
Switching
The EISC uses an 8K-address look-up table augmented with 128 entries of Content
Addressable Memory to eliminate hash-collision problems. An address-hashing
algorithm is used to update the table. Addresses are aged in about 300 seconds.
Illegal frames that are always discarded include bad CRC packets, runt packets (less
than 64 bytes) and oversized packets (greater than 1536 bytes).
6.3
Data Storage
Data storage buffer for Ethernet packets consists of 512 kB.
6.4
Data Forwarding
An entire Ethernet packet must be received before forwarding occurs. The EISC wire
speed forwarding rate (non-blocking) is 148,800 packets per second at 100 Mbps and
includes a special design to resolve head-of-line-blocking problems.
6.5
Flow Control
Each twisted-pair port automatically negotiates flow control and half- or full-duplex
operation. In full-duplex mode, the IEEE 802.3x PAUSE function is supported. In half-
duplex mode, the backpressure method is used. To prevent the connected repeater
from being partitioned due to excessive collisions, backpressure allows the forwarding
of one packet after 48 collisions.
6.6
Broadcast Storm Control
Using a storm-control counter, each port will pass 64 continuous broadcast packets
before dropping extra ones. The counter will reset every 800 ms or after receiving a
non-broadcast packet.
(All LEDs are tested each time the EISC is powered up.)
Figure 6 shows how Ports 3 and 4 (for
example) are numbered.