KSZ8842-16MVL TR Micrel, KSZ8842-16MVL TR Datasheet - Page 32

• Manufacturer Part Number: KSZ8842-16MVL TR
• Description: Ethernet ICs 2-Port Ethernet Switch/Repeater + Generic (8, 16-bit) bus interface(Lead Free)
• Manufacturer: Micrel

Specifications of KSZ8842-16MVL TR

• Rohs: yes
• Product: Ethernet Switches
• Package / Case: PQFP-128
• Mounting Style: SMD/SMT

Usage
LinkMD can be run at any time by making sure Auto MDIX has been disabled. To disable Auto-MDIX, write a ‘1’ to
P1CR4[10] for port 1 or P2CR4[10] for port 2 to enable manual control over the pair used to transmit the LinkMD pulse.
The self-clearing cable diagnostic test enable bit, P1VCT[15] for port 1 or P2VCT[15] for port 2 , is set to ‘1’ to start the
test on this pair.
When bit P1VCT[15] or P2VCT[15] returns to ‘0’, the test is complete. The test result is returned in bits P1VCT[14:13] or
P2VCT[14:13] and the distance is returned in bits P1VCT[8:0] or P2VCT[8:0]. The cable diagnostic test results are as
follows:
If P1VCT[14:13]=11 or P2VCT[14:13]=11, this indicates an invalid test, and occurs when the KSZ8842M is unable to shut
down the link partner. In this instance, the test is not run, as it is not possible for the KSZ8842M to determine if the
detected signal is a reflection of the signal generated or a signal from another source.
Cable distance can be approximated by the following formula:
P1VCT[8:0] X 0.4m for port 1 cable distance
P2VCT[8:0] X 0.4m for port 2 cable distance
This constant may be calibrated for different cabling conditions, including cables with a velocity of propagation that varies
significantly from the norm.
Functional Overview: MAC and Switch
Address Lookup
The internal lookup table stores MAC addresses and their associated information. It contains a 1K entry unicast address
learning table plus switching information.
The KSZ8842M is guaranteed to learn 1K addresses and distinguishes itself from hash-based lookup tables, which
depending on the operating environment and probabilities, may not guarantee the absolute number of addresses it can
learn.
Learning
The internal lookup engine updates its table with a new entry if the following conditions are met:
The lookup engine inserts the qualified SA into the table, along with the port number and time stamp. If the table is full, the
last entry of the table is deleted to make room for the new entry.
Migration
The internal lookup engine also monitors whether a station has moved. If a station has moved, it updates the table
accordingly. Migration happens when the following conditions are met:
The lookup engine updates the existing record in the table with the new source port information.
Aging
The lookup engine updates 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 lookup engine removes the record
from the table. The lookup engine constantly performs the aging process and continuously removes aging records. The
aging period is about 200 seconds. This feature can be enabled or disabled through Global Register SGCR1[10].
Micrel, Inc.
October 2007
1. The received packet's Source Address (SA) does not exist in the lookup table.
2. The received packet is good without receiving errors; the packet size is legal length.
1. The received packet's SA is in the table but the associated source port information is different.
2. The received packet is good without receiving errors; the packet size is legal length.
00 = Valid test, normal condition
01 = Valid test, open circuit in cable
10 = Valid test, short circuit in cable
11 = Invalid test, LinkMD failed
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KSZ8842-16/32 MQL/MVL/MVLI/MBL
M9999-102207-1.9