Datasheet

LAN8710A/LAN8710AI
DS00002164B-page 22  2016 Microchip Technology Inc.
3.1.4.2 Manchester Decoding
The output of the SQUELCH goes to the 10M RX block where it is validated as Manchester encoded data. The polarity
of the signal is also checked. If the polarity is reversed (local RXP is connected to RXN of the remote partner and vice
versa), the condition is identified and corrected. The reversed condition is indicated by the
XPOL bit of the Special Con-
trol/Status Indications Register. The 10M PLL is locked onto the received Manchester signal, from which the 20MHz
cock is generated. Using this clock, the Manchester encoded data is extracted and converted to a 10MHz NRZI data
stream. It is then converted from serial to 4-bit wide parallel data.
The 10M RX block also detects valid 10Base-T IDLE signals - Normal Link Pulses (NLPs) - to maintain the link.
3.1.4.3 10M Receive Data Across the MII/RMII Interface
For MII, the 4-bit data nibbles are sent to the MII block. In MII mode, these data nibbles are valid on the rising edge of
the 2.5 MHz RXCLK.
For RMII, the 2-bit data nibbles are sent to the RMII block. In RMII mode, these data nibbles are valid on the rising edge
of the RMII REF_CLK.
3.1.4.4 Jabber Detection
Jabber is a condition in which a station transmits for a period of time longer than the maximum permissible packet length,
usually due to a fault condition, which results in holding the TXEN input for a long period. Special logic is used to detect
the jabber state and abort the transmission to the line within 45ms. Once TXEN is deasserted, the logic resets the jabber
condition.
As shown in Section 4.2.2, "Basic Status Register," on page 45, the Jabber Detect bit indicates that a jabber condition
was detected.
3.2 Auto-negotiation
The purpose of the auto-negotiation function is to automatically configure the transceiver to the optimum link parameters
based on the capabilities of its link partner. Auto-negotiation is a mechanism for exchanging configuration information
between two link-partners and automatically selecting the highest performance mode of operation supported by both
sides. Auto-negotiation is fully defined in clause 28 of the IEEE 802.3 specification.
Once auto-negotiation has completed, information about the resolved link can be passed back to the controller via the
Serial Management Interface (SMI). The results of the negotiation process are reflected in the
Speed Indication bits of
the PHY Special Control/Status Register, as well as in the Auto Negotiation Link Partner Ability Register. The auto-nego-
tiation protocol is a purely physical layer activity and proceeds independently of the MAC controller.
The advertised capabilities of the transceiver are stored in the Auto Negotiation Advertisement Register. The default
advertised by the transceiver is determined by user-defined on-chip signal options.
The following blocks are activated during an Auto-negotiation session:
• Auto-negotiation (digital)
• 100M ADC (analog)
• 100M PLL (analog)
• 100M equalizer/BLW/clock recovery (DSP)
• 10M SQUELCH (analog)
• 10M PLL (analog)
• 10M Transmitter (analog)
When enabled, auto-negotiation is started by the occurrence of one of the following events:
• Hardware reset
• Software reset
• Power-down reset
• Link status down
• Setting the Restart Auto-Negotiate bit of the Basic Control Register