adm6992c Infineon Technologies Corporation, adm6992c Datasheet - Page 23

• Manufacturer Part Number: adm6992c
• Description: Two Port Bridge Fiber To Fast Ethernet Converter
• Manufacturer: Infineon Technologies Corporation

3.4.4
The address learning & filtering process forwards the incoming packets between bridged ports according to the
Destination Address (DA) as below.
1. If the DA is a UNICAST address and the address was found in the Address Table, the NINJA C/CX
2. If the DA is a UNICAST address and the address was not found, the NINJA C/CX (ADM6992C/CX) treats it as
3. If the DA is a Multicast address, the packet is forwarded across the bridge.
4. If the DA is PAUSE Command (01-80-C2-00-00-01), then this packet will be dropped by the NINJA C/CX
5. The NINJA C/CX (ADM6992C/CX) will forward by default or filter out the packet with DA of (01-80-C2-00-00-
3.4.5
Address aging is supported for topology changes such as an address moving from one port to the other. When
this happens, the NINJA C/CX (ADM6992C/CX) internally has 300 seconds timer, after which the address will be
“aged out” (removed) from the address table. Aging function can enabled/disabled by the user. Normally, disabling
the aging function is for security purposes.
3.4.6
The NINJA C/CX (ADM6992C/CX) implements the truncated exponential back off algorithm compliant to the 802.3
CSMA-CD standard. The NINJA C/CX (ADM6992C/CX) will restart the back off algorithm by choosing 0-9 collision
counts. The NINJA C/CX (ADM6992C/CX) resets the collision counter after 16 consecutive retransmitting trials.
3.4.7
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. The NINJA
C/CX (ADM6992C/CX) provides an option of 92 bit-time gaps in the EEPROM to prevent packet loss when Flow
Control is turned off and the clock P.P.M. value differs.
3.4.8
In store & forward mode, the NINJA C/CX (ADM6992C/CX) will discard all illegal frames such as small packets
(less than 64 bytes), oversized packets (greater than the value which is defined in Bit [13:0] of EEPROM register
03
In modified cut-through mode, the NINJA C/CX (ADM6992C/CX) will forward all received packets except for small
packets (less than 64 bytes).
In MII cut-through mode, the NINJA C/CX (ADM6992C/CX) will forward all received packets.
3.4.9
A Back Pressure function is supported for half-duplex operation. When the NINJA C/CX (ADM6992C/CX) cannot
allocate a received buffer for an incoming packet (buffer full), the device will transmit a jam pattern on the port,
thus forcing a collision. Back Pressure is disabled by DISBP which is set during RESETL assertion. A proprietary
Data Sheet
H
(ADM6992C/CX) will check the port number and act as follows:
a) If the port number is equal to the port on which the packet was received, the packet is discarded.
b) If the port number is different from the port on which the packet was received, the packet is forwarded across
a multicast packet and forwards it across the bridge.
(ADM6992C/CX). The NINJA C/CX (ADM6992C/CX) can issue and learn PAUSE commands.
00), discard the packet with DA of (01-80-C2-00-00-01), filter out the packet with DA of (01-80-C2-00-00-02 ~
01-80-C2-00-00-0F), and forward the packet with DA of (01-80-C2-00-00-10 ~ 01-80-C2-00-00-FF) decided
by EEPROM Reg. 0E
) and bad CRC. Dribbling packing with good CRC value will accept by NINJA C/CX (ADM6992C/CX).
the bridge.
Address Recognition and Packet Forwarding
Address Aging
Back off Algorithm
Inter-Packet Gap (IPG)
Illegal Frames
Half Duplex Flow Control
H
.
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Function Description
Rev. 1.02, 2005-11-25
ADM6992C/CX
Ninja C/CX