KSZ8842-PMBL AM TR Micrel Inc, KSZ8842-PMBL AM TR Datasheet - Page 21

• Manufacturer Part Number: KSZ8842-PMBL AM TR
• Description: 2-Port Ethernet Switch/Repeater + 32-bit/33MHz PCI Bus Interface( )
• Manufacturer: Micrel Inc

Specifications of KSZ8842-PMBL AM TR

• Number Of Primary Switch Ports: 2
• Internal Memory Buffer Size: 32
• Operating Supply Voltage (typ): 3.3V
• Fiber Support: Yes
• Integrated Led Drivers: Yes
• Phy/transceiver Interface: MII
• Power Supply Type: Analog/Digital
• Data Rate (typ): 10/100Mbps
• Vlan Support: Yes
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Mounting: Surface Mount
• Jtag Support: No
• Operating Supply Voltage (max): 3.5V
• Operating Supply Voltage (min): 3.1V
• Operating Temperature Classification: Industrial
• Data Rate: 100Mbps
• Lead Free Status / RoHS Status: Supplier Unconfirmed

Micrel, Inc.
KSZ8842-PMQL/PMBL
optimization. This is an ongoing process and self-adjusts against environmental changes such as temperature
variations.
Next, the equalized signal goes through a DC restoration and data conversion block. The DC restoration circuit is used
to compensate for the effect of baseline wander and to improve the dynamic range. The differential data conversion
circuit converts the MLT3 format back to NRZI. The slicing threshold is also adaptive.
The clock recovery circuit extracts the 125MHz clock from the edges of the NRZI signal. This recovered clock is then
used to convert the NRZI signal into the NRZ format. This signal is sent through the de-scrambler followed by the 4B/5B
decoder. Finally, the NRZ serial data is converted to the MII format and provided as the input data to the MAC.
PLL Clock Synthesizer (Recovery)
The internal PLL clock synthesizer generates 125MHz, 62.5MHz, 41.66MHz, and 25MHz clocks by setting the on-chip
bus speed control register OBCR for KSZ8842-PMQL/PMBL system timing. These internal clocks are generated from
an external 25MHz crystal or oscillator.
Note: Default setting is 25MHz in OBCR register, recommends the software driver to set it to 125MHz for best
performance.
Scrambler/De-scrambler (100BASE-TX Only)
The purpose of the scrambler is to spread the power spectrum of the signal to reduce electromagnetic interference
(EMI) and baseline wander. Transmitted data is scrambled through the use of an 11-bit wide linear feedback shift
register (LFSR). The scrambler generates a 2047-bit non-repetitive sequence, and the receiver then de-scrambles the
incoming data stream using the same sequence as at the transmitter.
10BASE-T Transmit
The 10BASE-T driver is incorporated with the 100BASE-TX driver to allow for transmission using the same magnetic.
They are internally wave-shaped and pre-emphasized into outputs with typical 2.3V amplitude. The harmonic contents
are at least 27dB below the fundamental frequency when driven by an all-ones Manchester-encoded signal.
10BASE-T Receive
On the receive side, input buffers and level detecting squelch circuits are employed. A differential input receiver circuit
and a phase-locked loop (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 pulse widths to
prevent noise 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 KSZ8842-PMQL/PMBL decodes a data frame. The receiver clock is
maintained active during idle periods in between data reception.
Power Management
The KSZ8842-PMQL/PMBL features a per port power-down mode. To save power, the user can power-down a port
that is not in use by setting bit 11 in either P1CR4 or P1MBCR register for port 1, and set bit 11 in either P2CR4 or
P2MBCR register for port 2. To bring the port back up, reset bit 11 in these registers.
In addition, there is a full switch power-down mode by PWRDN pin/ball 36. When this pin/ball is pulled-down, the entire
chip powers down. Transitioning this pin/ball from pull-down to pull-up results in a power up and chip reset.
MDI/MDI-X Auto Crossover
To eliminate the need for crossover cables between similar devices, the KSZ8842-PMQL/PMBL 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 the transmit and receive pairs
for the KSZ8842-PMQL/PMBL device. This feature is extremely useful when end users are unaware of cable types in
addition to saving on an additional uplink configuration connection. The auto-crossover feature can be disabled through
the port control registers.
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October 2007
M9999-100207-1.5