lxt971a Intel Corporation, lxt971a Datasheet - Page 33

• Manufacturer Part Number: lxt971a
• Description: 3.3v Dual-speed Fast Ethernet Phy Transceiver
• Manufacturer: Intel Corporation

3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
Datasheet
Document #: 249414
Revision #: 002
Rev. Date: August 7, 2002
Transmit Enable
The MAC must assert TX_EN the same time as the first nibble of preamble, and de-assert TX_EN
after the last bit of the packet.
Receive Data Valid
The LXT971A asserts RX_DV when it receives a valid packet. Timing changes depend on line
operating speed:
Carrier Sense
Carrier Sense (CRS) is an asynchronous output. It is always generated when a packet is received
from the line and in half-duplex mode when a packet is transmitted.
conditions for assertion of carrier sense, collision, and data loopback signals.
Carrier sense is not generated when a packet is transmitted and in full-duplex mode.
Error Signals
When LXT971A is in 100 Mbps mode and receives an invalid symbol from the network, it asserts
RX_ER and drives “1110” on the RXD pins.
When the MAC asserts TX_ER, the LXT971A drives “H” symbols out on the TPFOP/N pins.
Collision
The LXT971A asserts its collision signal, asynchronously to any clock, whenever the line state is
half-duplex and the transmitter and receiver are active at the same time.
conditions for assertion of carrier sense, collision, and data loopback signals.
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For 100BASE-TX links, RX_DV is asserted from the first nibble of preamble to the last nibble
of the data packet.
For 10BT links, the entire preamble is truncated. RX_DV is asserted with the first nibble of the
Start of Frame Delimiter (SFD) “5D” and remains asserted until the end of the packet.
LXT971A 3.3V Dual-Speed Fast Ethernet Transceiver
Table 10
Table 10
summarizes the
summarizes the
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