adm6995 ETC-unknow, adm6995 Datasheet - Page 27

• Manufacturer Part Number: adm6995
• Description: Port 10/100 Mb/s Single Chip Ethiernet Switch Controller
• Manufacturer: ETC-unknow

ADM6995L
ADMtek Inc.
3.15.4
3.15.5
3.15.6
3.15.7
3.15.8
3.15.9
The ADM6995L implements the truncated exponential back off algorithm compliant to
the 802.3 CSMA-CD standard. ADM6995L will restart the back off algorithm by
choosing 0-9 collision counts. The ADM6995L resets the collision counter after 16
consecutive retransmit trials.
IPG is the idle time between any two successive packets from the same port. The typical
number is 96 bits time. The value is 9.6us for 10Mbps ETHERNET, 960ns for 100Mbps
fast ETHERNET and 96ns for 1000M. ADM6995L provide option of 92 bit gap in
EEPROM to prevent packet lost when turn off Flow Control and clock P.P.M. value
difference.
The ADM6995L will discard all illegal frames such as runt packet (less than 64 bytes),
oversize packet (greater than 1518 or 1522 bytes) and bad CRC. Dribbling packing with
good CRC value will accept by ADM6995L. In case of bypass mode enabled,
ADM6995L will support tag and untagged packets with size up to 1522 bytes. In case of
non-bypass mode, ADM6995L will support tag packets up to 1526bytes, untagged
packets up to 1522bytes.
Back Pressure function is supported for half-duplex operation. When the ADM6995L
cannot allocate a receive buffer for an incoming packet (buffer full), the device will
transmit a jam pattern on the port, thus forcing a collision. Back Pressure is enabled by
the BPEN set during RESET asserting. An ADMtek proprietary algorithm is
implemented inside the ADM6995L to prevent back pressure function cause HUB
partitioned under heavy traffic environment and reduce the packet lost rate to increase the
whole system performance.
When full duplex port run out of its receive buffer, a PAUSE packet command will be
issued by ADM6995L to notice the packet sender to pause transmission. This frame
based flow control is totally compliant to IEEE 802.3x. ADM6995L can issue or receive
pause packet.
If Broadcast Storming filter is enable, the broadcast packets over the rising threshold
Back off Algorithm
Inter-Packet Gap (IPG)
Illegal Frames
Half Duplex Flow Control
Full Duplex Flow Control
Broadcast Storm filter
Function Description
3-11