LAN8810I-AKZE Datasheet, PDF (36/100 Pages) Microchip Technology – GMII 10/100/1000 Ethernet Transceiver with HP Auto-MDIX Support

GMII 10/100/1000 Ethernet Transceiver with HP Auto-MDIX Support
Datasheet
3.9.3
3.9.4
3.9.5
3.9.6
3.9.6.1
Isolate Mode
The device data paths may be electrically isolated from the GMII interface by setting the Isolate bit of
the Basic Control Register to “1”. In isolation mode, the transceiver does not respond to the TXD,
TXEN and TXER inputs, but does respond to management transactions.
Isolation provides a means for multiple transceivers to be connected to the same GMII interface without
contention. By default, the transceiver is not isolated (on power-up, Isolate=0).
Carrier Sense
The carrier sense signal is output on CRS. Carrier sense operation is defined in the IEEE 802.3u
standard. The PHY asserts carrier sense based only on receive activity whenever the PHY is either in
repeater mode or full-duplex mode. Otherwise, the PHY asserts carrier sense based on either transmit
or receive activity.
The carrier sense logic uses the encoded, unscrambled data to determine carrier activity status. It
activates carrier sense with the detection of 2 non-contiguous zeros within any 10 bit span. Carrier
sense terminates if a span of 10 consecutive ones is detected before a /J/K/ Start-of Stream Delimiter
pair. If an SSD pair is detected, carrier sense is asserted until either /T/R/ End–of-Stream Delimiter
pair or a pair of IDLE symbols is detected. Carrier is negated after the /T/ symbol or the first IDLE. If
/T/ is not followed by /R/, then carrier is maintained. Carrier is treated similarly for IDLE followed by
some non-IDLE symbol.
Collision Detect
A collision is the occurrence of simultaneous transmit and receive operations. The COL output is
asserted to indicate that a collision has been detected. COL remains active for the duration of the
collision. COL is changed asynchronously to both RXCLK and TXCLK. A collision can only occur in
half-duplex mode. The COL output becomes inactive during full duplex mode.
COL may be tested by setting the Collision Test bit of the Basic Control Register. This enables the
collision test. COL will be asserted within 512 bit times of TXEN rising and will be de-asserted within
4 bit times of TXEN falling.
In 10BASE-T mode, COL pulses for approximately 10 bit times (1us), 2us after each transmitted packet
(de-assertion of TXEN). This serves as the Signal Quality Error (SQE) signal and indicates that the
transmission was successful.
Link Integrity
This section details the establishment, maintenance and removal of links between the device and a
link partner in 1000BASE-T, 100BASE-TX and 10BASE-T modes. Link status is reported in the Link
Status bit of the Basic Status Register. The link status is also used to drive the device LEDs as
described in Section 3.9.1, "LEDs," on page 34.
Establishing and Maintaining a Link
Once a link state is determined via auto-negotiation, parallel detection, or forced operation, the device
and the link partner establish a link.
The completion of the auto-negotiation process is reported via the Auto-Negotiate Complete bit of the
Basic Status Register and issues an interrupt as described in Section 3.5, "Interrupt Management," on
page 26. The speed of the link is reported in the Speed Indication field of the PHY Special Control /
Status Register. The speed is also reported on the LED pins for any link.
Revision 1.0 (02-06-13)
36
DATASHEET
SMSC LAN8810/LAN8810i