KSZ8873FLLI Micrel Inc, KSZ8873FLLI Datasheet - Page 18

• Manufacturer Part Number: KSZ8873FLLI
• Description: IC ETHERNET SWITCH 3PORT 64LQFP
• Manufacturer: Micrel Inc

Specifications of KSZ8873FLLI

• Controller Type: Ethernet Switch Controller
• Interface: MII
• Voltage - Supply: 1.8V, 2.5V, 3.3V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Lead Free Status / Rohs Status: Supplier Unconfirmed
• Other names: 576-3632; KSZ8873FLLI

Micrel, Inc.
100BASE-FX Signal Detection
In 100BASE-FX operation, FXSD (fiber signal detect), input pin 15 and 63, is usually connected to the fiber transceiver SD (signal
detect) output pin. The fiber signal threshold can be selected by register 192 bit 7 and 6 respectively for port 2 and port 1 , When
FXSD is less than the threshold, no fiber signal is detected and a far-end fault (FEF) is generated. When FXSD is over the
threshold, the fiber signal is detected.
Alternatively, the designer may choose not to implement the FEF feature. In this case, the FXSD input pin is tied high to force
100BASE-FX mode.
100BASE-FX signal detection is summarized in the following table:
To ensure proper operation, a resistive voltage divider is recommended to adjust the fiber transceiver SD output voltage swing to
match the FXSD pin’s input voltage threshold.
100BASE-FX Far-End Fault
A far-end fault (FEF) occurs when the signal detection is logically false on the receive side of the fiber transceiver. The KSZ8873FLL
detects a FEF when its FXSD input is Fiber Signal Threshold. When a FEF is detected, the KSZ8873FLL signals its fiber link partner
that a FEF has occurred by sending 84 1’s followed by a zero in the idle period between frames.
By default, FEF is enabled. FEF can be disabled through register setting.
10BASE-T Transmit
The 10BASE-T driver is incorporated with the 100BASE-TX driver to allow for transmission using 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 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
KSZ8873MLL/FLL/RLL 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 KSZ8873MLL/FLL/RLL 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
KSZ8873MLL/FLL/RLL 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:
September 2010
Register 192 bit 7 (port 2), bit 6 (port 1)
1
0
RJ-45 Pins
1
2
3
6
MDI
Table 2. MDI/MDI-X Pin Definitions
Table 1. FX Signal Threshold
Signals
RD+
TD+
RD-
TD-
18
RJ-45 Pins
2.0V
1.2V
Fiber Signal Threshold at FXSD
1
2
3
6
MDI-X
Signals
RD+
TD+
RD-
TD-
KSZ8873MLL/FLL/RLL
M9999-092309-1.2