STE10A datasheet(21/82 Pages) STMICROELECTRONICS

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STE10/100A

Functional description

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Collision handling

The scheduling of re-transmissions are determined by a controlled randomization process

called “truncated binary exponential back-off”. At the end of enforcing a collision (jamming),

the STE10/100A delays before attempting to re-transmit the packet. The delay is an integer

multiple of slot time. The number of slot times to delay before the nth re-transmission

attempt is chosen as a uniformly distributed integer r in the range:

0 · r < 2k where k = min(n, 10)

3.5.2

Transceiver operation

The transceiver portion of the ste10/100a integrates the ieee802.3u compliant functions of

PCS (physical coding sub-layer), PMA (physical medium attachment) sub-layer, and PMD

(physical medium dependent) sub-layer for 100base-tx, and the ieee802.3 compliant

functions of manchester encoding/decoding and transceiver for 10base-t. All the functions

and operating schemes are described in the following sections.

100BASE-TX transmit operation

For 100BASE-TX transmissions, the STE10/100A transceiver provides the transmission

functions of PCS, PMA, and PMD for encoding of MII data nibbles into five-bit code-groups

(4B/5B), scrambling, serialization of scrambled code-groups, converting the serial NRZ code

into NRZI code, converting the NRZI code into MLT3 code, and then driving the MLT3 code

into the category 5 unshielded twisted pair cable through an isolation transformer with the

turns ratio of 1: 1.

Recommended transformers

HB626-1 from transpower technologies, 9410 prototype drive, suite #1, Reno, NV 89511.

Tel: (775) 852-0140 and H1102 from pulse engineering Inc., 12220 World Trade Drive, San

Diego, CA92128. Tel: (619) 674-8100.

Data code-groups encoder

In normal MII mode applications, the transceiver receives nibble type 4B data via the

TxD0~3 inputs of the MII. These inputs are sampled by the transceiver on the rising edge of

Tx-clk and passed to the 4B/5B encoder to generate the 5B code-group used by 100BASE-

TX.

Idle code-groups

In order to establish and maintain the clock synchronization, the transceiver must keep

transmitting signals to medium. The transceiver will generate Idle code-groups for

transmission when there is no actual data to be sent by MAC.

Start-of-stream delimiter-SSD (/J/K/)

In a transmission stream, the first 16 nibbles comprise the MAC preamble. In order to let a

network partner delineate the boundary of a data transmission sequence and to

authenticate carrier events, the transceiver will replace the first 2 nibbles of the MAC

preamble with /J/K/ code-groups.

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