RTL8201(L)
2002-01-18
Rev.1.04
22
7.8.2 10Base Tx/Rx
1)
10Base Transmit Function:
The 10Base transmit function is performed as follows: The transmit 4 bits nibbles(TXD[0:3])
clocked in 2.5MHz(TXC) is first feed to parallel to serial converter, then put the 10Mbps NRZ signal to Manchester
coding. The Manchester encoder converts the 10 Mbps NRZ data into a Manchester Encoded data stream for the TP
transmitter and adds a start of idle pulse (SOI) at the end of the packet as specified in IEEE 802.3. Then, the encoded data
stream is shaped by band- limited filter embedded in RTL8201(L) and then transmitted to TP line.
2)
10Base Receive function:
The 10Base receive function is performed as follows: In 10Base receive mode, The
Manchester decoder in RTL8201(L) converts the Manchester encoded data stream from the TP receiver into NRZ data by
decoding the data and stripping off the SOI pulse. Then, the serial NRZ data stream is converted to parallel 4 bit nibble
signal(RXD[0:3]).
7.9 Repeater Mode Operation
Setting bit 15 of register 17 to 1 or pulling the RPTR pin high will set the RTL8201(L) into repeater mode. In repeater mode,
the RTL8201(L) will assert CRS high only when receiving a packet. In NIC mode, the RTL8201(L) will assert CRS high both
in transmitting and receiving packets. If using the RTL8201(L) in a repeater, please set the RTL8201(L) to Repeater mode, and
if using the RTL8201(L) in a NIC or switch application, please set the default mode. NIC/Switch mode is the default setting
and has the RPTR pin pulled low or bit 15 of register 17 is set to 0.
7.10 Reset, Power, and Transmit Bias
The RTL8201(L) can be reset by pulling the RESTB pin low for about 10ms, then pulling the pin high. It can also be reset by
setting bit 15 of register 0 to 1, and then setting it back to 0. Reset will clear the registers and re-initialize them, and the media
interface will first disconnect and restart the auto-negotiation/parallel detection process.
Digital power and Analog power (including PLLVDD) need to be treated differently. Analog power needs sufficient
decoupling, a ferrite bead (100Ohm@100Mhz) and a capacitor to reduce the power noise.
The analog and digital Ground planes should be as large and intact as possible. If the ground plane is large enough, the analog
and digital grounds can be separated, which is a more ideal configuration. However, if the total ground plane is not sufficiently
large, partition of the ground plane is not a good idea. In this case, all the ground pins can be connected together to a larger
single and intact ground plane.
The RTSET pin must be pulled low by a 2.0K ohm resister with 1% accuracy to establish an accurate transmit bias, this will
affect the signal quality of the transmit waveform. Keep it’s circuitry away from other clock traces or transmit/receive paths to
avoid signal interference.
Tel: +49(0)234-9351135 · Fax: +49(0)234-9351137
E-MAIL:
http://www.
cornelius-consult.de
