lan8187 Standard Microsystems Corp., lan8187 Datasheet - Page 51

• Manufacturer Part Number: lan8187
• Description: Lan8187/lan8187i ?15kv Esd Protected Mii/rmii 10/100 Ethernet Transceiver With Hp Auto-mdix & Flexpwr Technology
• Manufacturer: Standard Microsystems Corp.

±15kV ESD Protected MII/RMII 10/100 Ethernet Transceiver with HP Auto-MDIX & flexPWR
Datasheet
SMSC LAN8187/LAN8187i
5.4
5.4.1
5.4.2
5.4.3
5.4.4
Carrier Sense
The carrier sense is output on CRS. CRS is a signal defined by the MII specification in the IEEE 802.3u
standard. The PHY asserts CRS based only on receive activity whenever the PHY is either in repeater
mode or full-duplex mode. Otherwise the PHY asserts CRS 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 RX_CLK and TX_CLK. The COL output becomes
inactive during full duplex mode.
COL may be tested by setting register 0, bit 7 high. This enables the collision test. COL will be asserted
within 512 bit times of TX_EN rising and will be de-asserted within 4 bit times of TX_EN falling.
In 10M mode, COL pulses for approximately 10 bit times (1us), 2us after each transmitted packet (de-
assertion of TX_EN). This is the Signal Quality Error (SQE) signal and indicates that the transmission
was successful. The user can disable this pulse by setting bit 11 in register 27.
Isolate Mode
The PHY data paths may be electrically isolated from the MII by setting register 0, bit 10 to a logic
one. In isolation mode, the PHY does not respond to the TXD, TX_EN and TX_ER inputs. The PHY
still responds to management transactions.
Isolation provides a means for multiple PHYs to be connected to the same MII without contention
occurring. The PHY is not isolated on power-up (bit 0:10 = 0).
Link Integrity Test
The LAN8187/LAN8187i performs the link integrity test as outlined in the IEEE 802.3u (Clause 24-15)
Link Monitor state diagram. The link status is multiplexed with the 10Mbps link status to form the
reportable link status bit in Serial Management Register 1, and is driven to the LINK LED.
The DSP indicates a valid MLT-3 waveform present on the RXP and RXN signals as defined by the
ANSI X3.263 TP-PMD standard, to the Link Monitor state-machine, using internal signal called
DATA_VALID. When DATA_VALID is asserted the control logic moves into a Link-Ready state, and
waits for an enable from the Auto Negotiation block. When received, the Link-Up state is entered, and
the Transmit and Receive logic blocks become active. Should Auto Negotiation be disabled, the link
integrity logic moves immediately to the Link-Up state, when the DATA_VALID is asserted.
Note that to allow the line to stabilize, the link integrity logic will wait a minimum of 330 μsec from the
time DATA_VALID is asserted until the Link-Ready state is entered. Should the DATA_VALID input be
negated at any time, this logic will immediately negate the Link signal and enter the Link-Down state.
When the 10/100 digital block is in 10Base-T mode, the link status is from the 10Base-T receiver logic.
Miscellaneous Functions
DATASHEET
51
TM
Technology
Revision 1.5 (01-10-08)