TNETE2004

MDIO-MANAGED QuadPHY

FOUR 10BASE-T PHYSICAL-LAYER INTERFACES

SPWS023D – OCTOBER 1996 – REVISED OCTOBER 1997

14

POST OFFICE BOX 655303

autopolarity

The TNETE2004 can sense and detect reversed polarity of its receiver inputs (e.g., due to incorrect cable

wiring). If, at any time, seven consecutive inverted link pulses are detected, then reversed polarity is assumed

and flagged by the POLOK bit in the TNETE2004_sts register (see Table 9). If automatic polarity correction is

selected by the SWAPPOLEN bit in the TNETE2004_ctl register (see Table 8), the TNETE2004 swaps its RCVP

and RCVN input for the affected PHY. Once a single correct link pulse is received, good polarity is assumed,

and the POLOK bit is set.

Automatic polarity correction is enabled by default after power on or reset. The polarity detect circuit must see

link pulses to detect the polarity of the receive pair, so, in instances of high network activity where link pulses

are sparse, there may be a slight delay before the correct polarity is established.

compatibility modes

To ease connection to third-party MACs, the TNETE2004 provides options to reverse the polarity of some device

pins. The compatibility mode is selected by the CMODE0 and CMODE1 pins, as defined in Table 2. The

TNETE2004 can be programmed through the MDIO to change the polarity of each SNI (like COL or RXCLK,

etc.) signal. Refer to Table 13 for more details on this function.

Table 2. Compatibility Mode Options

CMODE

PIN SIGNIFICANCE

Mode 1:

CMODE0 = Low

CMODE1 = Low

CRS high to indicate carrier detected

COL high to indicate collision

TXEN high to indicate valid data on TXD

Data on RXD valid on rising edge of RXCLK

Data on TXD valid on rising edge of TXCLK

RXD high when no data is being received

RXCLK is continuously running.

Mode 2:

CMODE0 = High

CMODE1 = Low

CRS low to indicate carrier detected

COL low to indicate collision

TXEN low to indicate valid data on TXD

Data on RXD valid on falling edge of RXCLK

Data on TXD valid on falling edge of TXCLK

RXD high when no data is being received

RXCLK runs for seven clocks after CRS is high,

then it stays high.

Mode 3:

CMODE0 = Low

CMODE1 = High

CRS high to indicate carrier detected

COL low to indicate collision

TXEN high to indicate valid data on TXD

Data on RXD valid on falling edge of RXCLK

Data on TXD valid on falling edge of TXCLK

RXD low when no data is being received

RXCLK runs for seven clocks after CRS is low,

then it stays high.

Mode 4:

CMODE0 = High

CMODE1 = High

CRS high to indicate carrier detected

COL high to indicate collision

TXEN high to indicate valid data on TXD

Data on RXD valid on rising edge of RXCLK

Data on TXD valid on rising edge of TXCLK

RXD low when no data is being received

RXCLK is continuously running.