KSZ8864RMN Datasheet, PDF (23/112 Pages) Micrel Semiconductor – Integrated 4-Port 10/100 Managed Switch with Two MACs MII or RMII Interfaces

Micrel, Inc.
KSZ8864RMN
Scrambler/De-Scrambler (100BASE-TX only)
The purpose of the scrambler is to spread the power spectrum of the signal in order to reduce EMI and baseline
wander. The data is scrambled through the use of an 11-bit wide linear feedback shift register (LFSR). This can
generate a 2047-bit non-repetitive sequence. The receiver will then de-scramble the incoming data stream with the
same sequence at the transmitter.
10BASE-T Transmit
The output 10BASE-T driver is incorporated into the 100BASE-T driver to allow transmission with the same
magnetics. They are internally wave-shaped and pre-emphasized into outputs with a typical 2.3V amplitude. The
harmonic contents are at least 27dB below the fundamental when driven by an all-ones Manchester-encoded signal.
10BASE-T Receive
On the receive side, input buffer and level detecting squelch circuits are employed. A differential input receiver circuit
and a PLL perform the decoding function. The Manchester-encoded data stream is separated into clock signal and
NRZ data. A squelch circuit rejects signals with levels less than 400mV or with short pulsewidths in order to prevent
noises at the RXP or RXM input from falsely triggering the decoder. When the input exceeds the squelch limit, the
PLL locks onto the incoming signal and the KSZ8864RMN decodes a data frame. The receiver clock is maintained
active during idle periods in between data reception.
MDI/MDI-X Auto Crossover
To eliminate the need for crossover cables between similar devices, the KSZ8864RMN supports HP Auto MDI/MDI-X and IEEE
802.3u standard MDI/MDI-X auto crossover. HP Auto MDI/MDI-X is the default.
The auto-sense function detects remote transmit and receive pairs and correctly assigns transmit and receive pairs for the
KSZ8898MQ/TMQ device. This feature is extremely useful when end users are unaware of cable types, and also, saves on an
additional uplink configuration connection. The auto-crossover feature can be disabled through the port control registers, or MIIM
PHY registers. The IEEE 802.3u standard MDI and MDI-X definitions are:
MDI
RJ-45 Pins Signals
1
TD+
2
TD-
3
RD+
6
RD-
MDI-X
RJ-45 Pins
1
Signals
RD+
2
RD-
3
TD+
6
TD-
Table 1. MDI/MDI-X Pin Definitions
September 2011
23
M9999-092011-1.4