SLXT973QC Cortina Systems Inc, SLXT973QC Datasheet - Page 26

• Manufacturer Part Number: SLXT973QC
• Manufacturer: Cortina Systems Inc

Specifications of SLXT973QC

• Lead Free Status / Rohs Status: Not Compliant

LXT973 Transceiver
Datasheet
249426, Revision 6.0
13 July 2007
3.3.4
3.3.5
3.3.6
3.3.7
3.3.7.1
3.3.7.2
Cortina Systems
Carrier Sense
Carrier Sense (CRS) is an asynchronous output. CRS is generated when a packet is
received from the line regardless of duplex mode, and for a transmission to the line in half-
duplex mode.
sense, collision, and data loopback signals. Carrier sense is not generated when a packet
is transmitted in full-duplex mode.
For 100BASE-TX and 100BASE-FX links, a Start-of-Stream Delimiter (SSD) or /J/K/
symbol pair causes assertion of carrier sense (CRS). An End-of-Stream Delimiter (ESD),
or /T/R/ symbol pair causes de-assertion of CRS. The PMA layer also de-asserts CRS if
IDLE symbols are received without /T/R/. In this event, the RXER bit in the RX Status
Frame is asserted for one clock cycle when CRS is de-asserted.
For 10BASE-T links, CRS assertion is based on receipt of a valid preamble, and de-
assertion is based on receipt of an End-of-Frame (EOF) marker.
Error Signals
When the LXT973 Transceiver is in 100 Mbps mode and receives an invalid symbol from
the network, it asserts RXER and drives “1110” on the RXD pins.
When the MAC asserts TXER, the LXT973 Transceiver drives “H” symbols out on the
DPAP/N_0 or
DPAP/N_1 pins.
Collision
The LXT973 Transceiver asserts its collision signal, asynchronously to any clock, when
the line state is half-duplex and the transmitter and receiver are active at the same time.
Table 8 on page 27
and data loopback signals.
Loopback
The LXT973 Transceiver provides two loopback functions, operational and test (see
Table 8 on page
Operational Loopback
Operational loopback is provided for 10 Mbps half-duplex links when Register bit 16.8 = 0.
Data transmitted by the MAC (TXD) is looped back on the receive side of the MII (RXD).
Operational loopback is not provided for 100 Mbps links, full-duplex links, or when
Register bit 16.8 = 1.
Test Loopback
A test loopback function is provided for diagnostic testing of the LXT973 Transceiver.
During test loopback, twisted-pair and fiber interfaces are disabled. Data transmitted by
the MAC is internally looped back by the LXT973 Transceiver and returned to the MAC
(see
®
• For 10BASE-T links, the entire preamble is truncated. RXDV is asserted with the first
LXT973 10/100 Mbps Dual-Port Fast Ethernet PHY Transceiver
nibble of the Start-of-Frame Delimiter (SFD) “5D” and remains asserted until the end
of the packet.
Figure
4).
Table 8 on page 27
27). Loopback paths are shown in
summarizes the conditions for assertion of carrier sense, collision,
summarizes the conditions for assertion of carrier
Figure 4 on page
27.
3.3 MII Operation
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