L80227 LSI, L80227 Datasheet - Page 133

• Manufacturer Part Number: L80227
• Manufacturer: LSI

Specifications of L80227

• Lead Free Status / RoHS Status: Not Compliant

A.6.4 Receive Output Enable
A.7 Repeater Applications
A.7.1 MII Based Repeaters
A.7.2 Clocks
The receive output enable pin, RX_EN, forces the receive and collision
MII outputs into the high-impedance state. More specifically, when
RX_EN is deasserted, the RX_CLK, RXD[3:0], RX_DV, RX_ER, and
COL pins are placed in a high-impedance state.
RX_EN can be used to “wire OR” the outputs of many L80227 devices
in multiport applications where only one device may be receiving at a
time, such as in a repeater application. Monitoring the CRS pin from
each individual port enables the repeater to assert RX_EN only to that
L80227 device that is receiving data. The method reduces, by eight per
device, the number of pins and PCB traces a repeater core IC requires.
Using the standard MII as the interface to the repeater core allows the
L80227 to be used as the physical interface for MII based repeaters. For
most repeaters, it is necessary to disable the internal CRS loopback.
For some particular types of repeaters, it may be desirable to either
enable or disable AutoNegotiation, force Half-Duplex operation, and
enable either 100 Mbits/s or 10 Mbits/s operation. Setting the appropriate
bits in the MI serial port Control register can configure these modes.
The MII requires 16 signals between the L80227 and a repeater core.
The MII signal count to a repeater core is 16 multiplied by the number of
ports, which can be quite large. The signal count between the L80227
and a repeater core can be reduced by eight per device if the receive
output pins are shared and the RX_EN is used to enable only that port
where CRS is asserted. Refer to the
Enable,” page A-11
Normally, transmit data over the MII is clocked into the L80227 with
edges from the TX_CLK output clock. It may be desirable or necessary
in some repeater applications to clock in the transmit data from a master
Repeater Applications
Copyright © 2000, 2001, 2002 by LSI Logic Corporation. All rights reserved.
for more details about RX_EN.
Section A.6.4, “Receive Output
A-11