Micrel, Inc.
KSZ9021RL/RN
Pair- Swap, Alignment, and Polarity Check
In 1000Base-T mode, the KSZ9021RL/RN
•
•
Detects incorrect channel order and automatically restore the pair order for the A, B, C, D pairs (four channels)
Supports 50±10ns difference in propagation delay between pairs of channels in accordance with the IEEE 802.3
standard, and automatically corrects the data skew so the corrected 4-pairs of data symbols are synchronized
Incorrect pair polarities of the differential signals are automatically corrected for all speeds.
Wave Shaping, Slew Rate Control and Partial Response
In communication systems, signal transmission encoding methods are used to provide the noise-shaping feature and to
minimize distortion and error in the transmission channel.
•
For 1000Base-T, a special partial response signaling method is used to provide the band-limiting feature for the
transmission path.
•
•
For 100Base-TX, a simple slew rate control method is used to minimize EMI.
For 10Base-T, pre-emphasis is used to extend the signal quality through the cable.
PLL Clock Synthesizer
The KSZ9021RL/RN generates 125MHz, 25MHz and 10MHz clocks for system timing. Internal clocks are generated from
the external 25MHz crystal or reference clock.
Auto-Negotiation
The KSZ9021RL/RN conforms to the auto-negotiation protocol, defined in Clause 28 of the IEEE 802.3 Specification.
Auto-negotiation allows UTP (Unshielded Twisted Pair) link partners to select the highest common mode of operation.
During auto-negotiation, link partners advertise capabilities across the UTP link to each other, and then compare their own
capabilities with those they received from their link partners. The highest speed and duplex setting that is common to the
two link partners is selected as the mode of operation.
The following list shows the speed and duplex operation mode from highest to lowest.
•
•
•
•
•
•
Priority 1: 1000Base-T, full-duplex
Priority 2: 1000Base-T, half-duplex
Priority 3: 100Base-TX, full-duplex
Priority 4: 100Base-TX, half-duplex
Priority 5: 10Base-T, full-duplex
Priority 6: 10Base-T, half-duplex
If auto-negotiation is not supported or the KSZ9021RL/RN link partner is forced to bypass auto-negotiation for 10Base-T
and 100Base-TX modes, then the KSZ9021RL/RN sets its operating mode by observing the input signal at its receiver.
This is known as parallel detection, and allows the KSZ9021RL/RN to establish a link by listening for a fixed signal
protocol in the absence of auto-negotiation advertisement protocol.
The auto-negotiation link up process is shown in the following flow chart.
M9999-101309-1.1
October 2009
26
MICREL [ MICREL SEMICONDUCTOR ]
