Datasheet

KSZ8041TL/FTL/MLL
DS00002436B-page 20  2017 Microchip Technology Inc.
3.6 10BASE-T Receive
On the receive side, input buffer and level detecting squelch circuits are employed. A differential input receiver circuit
and a PLL performs 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 400 mV or with short pulse widths to prevent noise at
the RX+ and RX– inputs from falsely trigger the decoder. When the input exceeds the squelch limit, the PLL locks onto
the incoming signal and the KSZ8041TL/FTL/MLL decodes a data frame. The receive clock is kept active during idle
periods in between data reception.
3.7 SQE and Jabber Function (10BASE-T Only)
In 10BASE-T operation, a short pulse is put out on the COL pin after each frame is transmitted. This SQE Test is required
as a test of the 10BASE-T transmit/receive path. If transmit enable (TXEN) is high for more than 20 ms (jabbering), the
10BASE-T transmitter is disabled and COL is asserted high. If TXEN is then driven low for more than 250 ms, the
10BASE-T transmitter is re-enabled and COL is de-asserted (returns to low).
3.8 Auto-Negotiation
The KSZ8041TL/FTL/MLL conforms to the auto-negotiation protocol, defined in Clause 28 of the IEEE 802.3u specifi-
cation. Auto-negotiation is enabled by either hardware pin strapping (pin 42) or software (register 0h bit 12).
Auto-negotiation allows unshielded twisted pair (UTP) link partners to select the highest common mode of operation.
Link partners advertise their capabilities 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: 100BASE-TX, full-duplex
• Priority 2: 100BASE-TX, half-duplex
• Priority 3: 10BASE-T, full-duplex
• Priority 4: 10BASE-T, half-duplex
If auto-negotiation is not supported or the KSZ8041TL/FTL/MLL link partner is forced to bypass auto-negotiation, the
KSZ8041TL/FTL/MLL sets its operating mode by observing the signal at its receiver. This is known as parallel detection,
and allows the KSZ8041TL/FTL/MLL to establish link by listening for a fixed signal protocol in the absence of auto-nego-
tiation advertisement protocol.
The auto-negotiation link up process is shown in the following flow chart.