STE100P_06 Datasheet, PDF (17/31 Pages) STMicroelectronics – 10/100 FAST ETHERNET 3.3V TRANSCEIVER

STE100P
7.5 Loop-back Operation
The STE100P provides internal loop-back option for both the 100Base-TX and 10Base-T operations. Set-
ting bit 14 of PR0 register to 1 can enable the loop-back option. In this loop-back operation, the txp/txn
and rxp/rxn lines are isolated from the media. The STE100P also provides remote loop-back operation for
100Base-TX operation. Setting bit 9 of PR19 register to 1 enables the remote loop-back operation.
In the 100Base-TX internal loop-back operation, the data comes from the transmit output of NRZ to NRZI
converter then loop-back to the receive path into the input of NRZI to NRZ converter.
In the 100Base-TX remote loop-back operation, the data is received from rxp/rxn pins through receive
path to the output of data and clock recover and then loop-back to the input of NRZI to MLT3 converter of
transmit path then transmit out to the medium via the transmit line drivers.
In the 10Base-T loop-back operation, the data is through transmit path and loop-back from the output of
the Manchester encoder into the input of Phase Lock Loop circuit of receive path.
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 ig-
nored and carrier 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, col-
lision 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 partner’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-
Negotiation function will proceed. Otherwise, the Auto-Negotiation will not occur until the bit 12 of PR0 reg-
ister is set to 1. When Auto-Negotiation is disabled, then the Network Speed and Duplex Mode are select-
ed by programming 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 read-
ing and writing device registers. Power Down mode can be exited by clearing bit 11 of register PR0 or by
a hardware or software reset (setting PR0:15=1).
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