adm6992c Infineon Technologies Corporation, adm6992c Datasheet - Page 22

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

3.3.2
The NINJA C/CX (ADM6992C/CX) begins to forward the received packet when it receives the first 64 bytes of the
packet. The latency is about 512 bits time width. The NINJA C/CX (ADM6992C/CX) will not forward fragment
packets. The MAC address learning & filtering should be disabled in this mode, because the received packets may
be corrupted. The maximum packet length is up to 9216 bytes in this mode. The maximum packet length is defined
in Bit [13:0] of EEPROM register 03
3.3.3
The NINJA C/CX (ADM6992C/CX) begins to forward the received packet at the beginning of the received packet.
It provides the minimum latency in this mode. The maximum packet length is 9216 bytes if the clock difference
between MII receive clock and MII transmit clock is 200Ppm.
3.4
3.4.1
The NINJA C/CX (ADM6992C/CX) adopts 4-way associative hash architecture to store the MAC address table. It
can store up to a maximum 1K of MAC addresses.
In store & forward mode, the NINJA C/CX (ADM6992C/CX) receives incoming packets from one of its ports,
searches in the Address Table for the Destination MAC Address, and then forwards the packet to the other port,
if appropriate. If the destination address is not found in the address table, the NINJA C/CX (ADM6992C/CX) treats
the packet as a broadcast packet and forwards the packet to the other ports. If the destination port is the same
with the port where the packet received from, the NINJA C/CX (ADM6992C/CX) treats the packet as a local traffic
packet and discards it.
3.4.2
The NINJA C/CX (ADM6992C/CX) searches for the Source Address (SA) of an incoming packet in the Address
Table and acts as below:
1. The NINJA C/CX (ADM6992C/CX) automatically learns the port number of attached network devices by
2. If the SA was not found in the Address Table (a new address), the NINJA C/CX (ADM6992C/CX) waits until
3. If the SA was found in the Address Table, then the aging value of each corresponding entry will be reset to 0
4. When the DA is in PAUSE mode, then the learning process will be disabled automatically by the NINJA C/CX
3.4.3
The NINJA C/CX (ADM6992C/CX) supports two types of hash algorithms for address learning & filtering. The first
is the CRC-CCITT polynomial method. The 48 bits MAC address is reduced to a 16 bits CRC hash value. Bit [7:0]
of the CRC are used to index the 1K address table. The CRC-CCITT polynomial is
The second is the direct-map method. The 48-bit MAC address is mapped into a 8 bits address spaced by XOR-
method to index the 1K address table.
The hash type can be selected by using bit [15] of EEPROM register 03
Data Sheet
examining the Source MAC Address of all incoming packets at wire speed
the end of the packet (non-error packet) and updates the Address Table
(ADM6992C/CX)
Modified Cut-through Mode
MII cut-through Mode
Basic Operations
MAC Address Learning & Filtering
Address Learning
Hash Algorithm
H
.
22
H
.
Function Description
Rev. 1.02, 2005-11-25
ADM6992C/CX
Ninja C/CX