ST802RT1B datasheet(40/58 Pages) STMICROELECTRONICS

40 / 58 page

Device operation

ST802RT1A, ST802RT1B

40/58

Doc ID 17049 Rev 1

7.3

10Base-T transmit operation

In 10Base-T, the device's TX channel includes the parallel-to-serial converter, NRZ to

manchester encoder, link pulse generation, and an internal physical ethernet wire interface

(Phy). It also provides collision detection and SQE test for half-duplex application.

RMII mode: Uses a reference clock (SCLK) of 50 MHz. The value on txd[1:0] must be valid

such that txd[1:0] may be sampled every 10th cycle yielding the correct frame data. To

achieve this, the dibits should be repeated 10 times.

7.4

10Base-T receive operation

The 10Base-T RX channel contains the Phy, SMART squelch circuits, clock recovery

circuits, link pulse detector, manchester-to-NRZ decoder and serial-to-parallel converter.

manchester decoding is performed on the data stream.

RMII mode: Dibits are repeated 10 times so that any repeated dibit may be sampled on the

10 Mb clock edge.

7.5

Loop-back operation

The ST802RT1x provides an internal loop-back option for both 100Base-TX and 10Base-T

operations. Setting bit 14 of the RN00 register to 1 enables the loop-back option. In the loop-

back operation, the txp/txn and rxp/rxn lines are isolated from the media. In 100Base-TX

internal loop-back operation, the data comes from the transmit output of the NRZ to NRZI

converter then loop back to the receive path into the input of NRZI to NRZ converter.

In 10Base-T loop-back operation, the data is sent through the transmit path and loop back

from the output of the manchester encoder into the input of phase lock loop circuit of the

receive path.

7.6

Full-duplex and half-duplex operation

The ST802RT1x can operate in either full-duplex or half-duplex network applications. In full-

duplex, both transmit and receive can be operated simultaneously. In full-duplex mode, the

collision (COL) signal is meaningless and carrier sense (CRS) signal is asserted only when

the ST802RT1x is receiving.

In half-duplex mode, only transmit or receive can be operated at one time. In half-duplex

mode, the collision signal is asserted when the transmit and receive signals collide and the

carrier sense asserted during transmission and reception.

7.7

Auto-negotiation operation

The auto-negotiation function is designed to provide the means to exchange information

between the ST802RT1x and the network partner to automatically configure both to take

maximum advantage of their abilities, and both are setup accordingly. The auto-negotiation

function can be controlled through auto-negotiation enable bit 12 of the RN00 register, or the

an_en strap pin 27.

ST802RT1B 数据表(PDF) 40 Page - STMicroelectronics

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