SLXT973QE Cortina Systems Inc, SLXT973QE Datasheet - Page 56

• Manufacturer Part Number: SLXT973QE
• Manufacturer: Cortina Systems Inc

Specifications of SLXT973QE

• Lead Free Status / RoHS Status: Not Compliant

LXT973 Transceiver
Datasheet
249426, Revision 6.0
13 July 2007
7.0
Cortina Systems
Auto-MDI/MDIX
Twisted-pair Ethernet PHYs must be correctly configured for MDI or MDIX operation to
inter operate. This has historically been accomplished using special patch cables,
magnetics pinouts, or PCB wiring.
The LXT973 Transceiver PHY supports the automatic MDI/MDIX configuration originally
developed for 1000BASE-T and standardized in IEEE 802.3u, section 40. A manual
configuration (for example, non-automatic) is still possible using configuration register
bits. The automatic MDI/MDIX function is not intended for fiber applications.
The automatic MDI/MDIX state machine facilitates switching of the twisted-pair input
signals (DPBP/N_0 and DPAP/N_1) with the twisted-pair output signals (DPAP/N_0 and
DPBP/N_1), respectively, prior to the auto-negotiation mode of operation. This is done so
that FLPs can be transmitted and received in compliance with Clause 28, Auto-
Negotiation specifications.
The correct polarization of the crossover circuit is determined by an algorithm that controls
the switching function. This algorithm uses an 11-bit Linear Feedback Shift Register
(LFSR) to create a pseudo-random sequence that each end of the link uses to determine
its proposed configuration.
After selecting MDI or MDIX, the node waits for a specified amount of time, while
evaluating its receive channel, to determine whether the other end of the link is sending
link pulses or PHY-dependent data. If link pulses or PHY-dependent data are detected, it
remains in that configuration. If link pulses or PHY-dependent data are not detected, it
increments its LFSR and makes a decision to switch based on the value of the next bit.
The state machine does not move from one state to another while link pulses are being
transmitted.
®
LXT973 10/100 Mbps Dual-Port Fast Ethernet PHY Transceiver
7.0 Auto-MDI/MDIX
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