KSZ8895 INFINEON [Infineon Technologies AG], KSZ8895 Datasheet - Page 32

• Manufacturer Part Number: KSZ8895
• Description: Integrated 5-Port 10/100 Managed Ethernet Switch with MII/RMII interface
• Manufacturer: INFINEON [Infineon Technologies AG]

Micrel, Inc.
Migration
The internal look-up engine also monitors whether a station is moved. If this occurs, it updates the table accordingly.
Migration happens when the following conditions are met:
The look-up engine will update the existing record in the table with the new source port information.
Aging
The look-up engine will update the time stamp information of a record whenever the corresponding SA appears. The
time stamp is used in the aging process. If a record is not updated for a period of time, the look-up engine will
remove the record from the table. The look-up engine constantly performs the aging process and will continuously
remove aging records. The aging period is 300 +/- 75 seconds. This feature can be enabled or disabled through
Register 3 or by external pull-up or pull-down resistors on LED[5][2]. See “Register 3” section.
Forwarding
The KSZ8895MQ/RQ/FMQ will forward packets using an algorithm that is depicted in the following flowcharts. Figure
6 shows stage one of the forwarding algorithm where the search engine looks up the VLAN ID, static table, and
dynamic table for the destination address, and comes up with “port to forward 1” (PTF1). PTF1 is then further
modified by the spanning tree, IGMP snooping, port mirroring, and port VLAN processes to come up with “port to
forward 2” (PTF2), as shown in Figure 7. This is where the packet will be sent.
KSZ8895MQ/RQ/FMQ will not forward the following packets:
• Error packets. These include framing errors, FCS errors, alignment errors, and illegal size packet errors.
• 802.3x pause frames. The KSZ8895MQ/RQ/FMQ will intercept these packets and perform the appropriate actions.
• “Local” packets. Based on destination address (DA) look-up. If the destination port from the look-up table matches
Switching Engine
The KSZ8895MQ/RQ/FMQ features a high-performance switching engine to move data to and from the MAC’s,
packet buffers. It operates in store and forward mode, while the efficient switching mechanism reduces overall
latency. The KSZ8895MQ/RQ/FMQ has a 64kB internal frame buffer. This resource is shared between all five ports.
There are a total of 512 buffers available. Each buffer is sized at 128B.
Media Access Controller (MAC) Operation
The KSZ8895MQ/RQ/FMQ strictly abides by IEEE 802.3 standards to maximize compatibility.
Inter-Packet Gap (IPG)
If a frame is successfully transmitted, the 96-bit time IPG is measured between the two consecutive MTXEN. If the
current packet is experiencing collision, the 96-bit time IPG is measured from MCRS and the next MTXEN.
Backoff Algorithm
The KSZ8895MQ/RQ/FMQ implements the IEEE Std. 802.3 binary exponential back-off algorithm, and optional
“aggressive mode” back off. After 16 collisions, the packet will be optionally dropped depending on the chip
configuration in Register 3. See “Register 3.”
Late Collision
If a transmit packet experiences collisions after 512-bit times of the transmission, the packet will be dropped.
Illegal Frames
The KSZ8895MQ/RQ/FMQ discards frames less than 64 bytes and can be programmed to accept frames up to 1536
bytes in Register 4. For special applications, the KSZ8895MQ/RQ/FMQ can also be programmed to accept frames
up to 1916 bytes in Register 4. Since the KSZ8895MQ/RQ/FMQ supports VLAN tags, the maximum sizing is
adjusted when these tags are present.
January 2011
the port where the packet was from, the packet is defined as “local.”
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The received packet’s SA is in the table but the associated source port information is different.
The received packet is good; the packet has no receiving errors and is of legal length.
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KSZ8895MQ/RQ/FMQ
M9999-012011-1.2