TNETX3100 datasheet(13/80 Pages) TI1

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TNETX3100

ThunderSWITCH™ 10-PORT 10-/100-MBIT/S ETHERNET™ SWITCH

SPWS031D – JUNE 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

10-Mbit/s and 10-/100-Mbit/s MAC interfaces (ports 00–09)

The following section illustrates the similarities between the 10-Mbit/s and 10-/100-Mbit/s MAC interfaces. All

network data flows through either the 10-Mbit/s interface or 10-/100-Mbit/s interface.

data reception

receive arbitration

Receive arbitration raises the priority of received frames over pending transmit. Active transmissions are given

highest priority. This makes it less likely that frames will be lost during heavy traffic load. For correct TNETX3100

operation, the RXARB bit (bit 5) must be set in the SIO register.

receive control

Receiver control is partitioned into two blocks:

The frame control block schedules all receive operations, i.e., detection and removal of the preamble,

extraction of the addresses and frame length, data handling, and cyclic redundancy check (CRC) checking.

Also included is a jabber-detection timer to detect frames being received on the network that exceed the

maximum allowable length.

The FIFO control block places the received data in the FIFO buffers while also detecting and flagging

erroneous data conditions in the flag byte.

TNETX3100 MXXDUPLEX terminals

The MXXDUPLEX terminals are implemented as inputs with active pulldown circuitry, producing a

pseudo-bidirectional terminal.

An external PHY can weakly drive the DUPLEX line high, indicating an intention for duplex operation. The

TNETX3100 can override this DUPLEX terminal input by pulling the line low. This is detected by the PHY, which

monitors the sense of the DUPLEX signal, causing it to operate in half-duplex mode. Thus, the TNETX3100 can

force the PHY into half-duplex operation when desired (during testing, for example). See Figure 1.

PHY

Resistor

Duplex Signal

Weakly Driven

Duplex Signal

Sense Feedback

TNETX3100

Duplex

GND

Active

Pulldown

Input

MXXDUPLEX

Forced

Half-Duplex (HD)

Signal

Figure 1. MXXDUPLEX Signal Connection

If the PHY is driven only in half-duplex operation, a pulldown resistor should be permanently attached to the

DUPLEX signal. If the PHY is operated in full duplex (with the option of the TNETX3100 forcing half duplex),

a pullup resistor should be placed on the DUPLEX signal.

TNETX3100 数据表(PDF) 13 Page - Texas Instruments

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