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STE100P

7.6 Full Duplex and Half Duplex Operation

The STE100P can operate for either full duplex or half duplex network application. In full duplex, both transmit

and receive can be operated simultaneously. Under full duplex mode, collision(COL) signal is ignored and car-

rier sense(CRS) signal is asserted only when the STE100P is receiving.

In half duplex mode, either transmit or receive can be operated at one time. Under half duplex mode, collision

signal is asserted when transmit and receive signals collided and 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 STE100P

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 ANE, bit 12 of the PR0 register,

or the MF0 pin 5.

Auto-Negotiation exchanges information with the network partner using the Fast Link Pulses(FLPs) - a burst of

link pulses. There are 16 bits of signaling information contained in the burst pulses to advertise all remote part-

ner’s capabilities which are determined by the register of PR4. According to this information they find out their

highest common capability by following the priority sequence as below:

1. 100BASE-TX full duplex

2. 100BASE-TX half duplex

3. 10BASE-T full duplex

4. 10BASE-T half duplex

During power-up or reset, if Auto-Negotiation is found enabled then FLPs will be transmitted and the Auto-Ne-

gotiation function will procede. Otherwise, the Auto-Negotiation will not occur until the bit 12 of PR0 register is

set to 1. When Auto-Negotiation is disabled, then the Network Speed and Duplex Mode are selected by pro-

gramming PR0 register.

7.8 Power Down Operation

To reduce the power consumption, the STE100P is designed with a power down feature, which can save the power

consumption significantly. Since the power supply of the 100BASE-TX and 10BASE-T circuits are separated, the

STE100P can turn off the circuit of either the 100BASE-TX or 10BASE-T when the other one of them is operating.

There is also a Power Down mode which can be selected by PDEN in register PR0 bit 11. During the Power Down

mode, TXP/TXN outputs and all LED outputs are 3-stated, and the MII interface is isolated. During Power Down mode

the MII management interface is still available for reading and writing device registers. Power Down mode can be ex-

ited by clearing bit 11 of register PR0 or by a hardware or software reset (setting PR0:15=1).

7.9 LED Display Operation

The STE100P provides 2 functions for the LED pins, the detail descriptions about the operation are described

in the PIN Description section, and as follows.

• First mode - 3 LED displays for:

• 100Mbps (on) or 10Mbps (off)

• Link (Stays on when link okay) or Activity (Blinks at 10Hz when receiving or transmitting, but not collision)

• FD (Stays on when in Full duplex mode) or Collision (Blinks at 20Hz when a collision occurs)

• Second mode – 4 LED displays for:

• 100 Link (On when 100M link is okay)

• 10 Link (On when 10M link is okay)

• Activity (Blinks at 10Hz when receiving or transmitting)

• FD (Stays on when in Full duplex mode) or Collision (Blinks at 20Hz when a collision occurs)