Datasheet

start of packet end of packet

<150 ns <150 ns >150 ns

VSQ+

VSQ-

VSQ-(reduced)

VSQ+(reduced)

DP83620

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SNLS339C –JANUARY 2011–REVISED APRIL 2013

Valid data is considered to be present until the squelch level has not been generated for a time longer

than 150 ns, indicating the End of Packet. Once good data has been detected, the squelch levels are

reduced to minimize the effect of noise causing premature End of Packet detection.

The receive squelch threshold level can be lowered for use in longer cable or STP applications. This is

achieved by configuring the SQUELCH bits (11:9) in the 10BTSCR register (0x1A).

Figure 7-3. 10BASE-T Twisted Pair Smart Squelch Operation

7.4.3 Collision Detection and SQE

When in Half Duplex, a 10BASE-T collision is detected when the receive and transmit channels are active

simultaneously. Collisions are reported by the COL signal on the MII. Collisions are also reported when a

jabber condition is detected.

The COL signal remains set for the duration of the collision. If the ENDEC is receiving when a collision is

detected it is reported immediately (through the COL pin).

When heartbeat is enabled, approximately 1 µs after the transmission of each packet, a Signal Quality

Error (SQE) signal of approximately 10-bit times is generated to indicate successful transmission. SQE is

reported as a pulse on the COL signal of the MII.

The SQE test is inhibited when the PHY is set in full duplex mode. SQE can also be inhibited by setting

the HEARTBEAT_DIS bit (1) in the 10BTSCR register (0x1A).

7.4.4 Carrier Sense

Carrier Sense (CRS) may be asserted due to receive activity once valid data is detected via the squelch

function.

For 10 Mb/s Half Duplex operation, CRS is asserted during either packet transmission or reception.

For 10 Mb/s Full Duplex operation, CRS is asserted only during receive activity.

CRS is deasserted following an end of packet.

7.4.5 Normal Link Pulse Detection/Generation

The link pulse generator produces pulses as defined in the IEEE 802.3 10BASE-T standard. Each link

pulse is nominally 100 ns in duration and transmitted every 16 ms in the absence of transmit data.

Link pulses are used to check the integrity of the connection with the remote end. If valid link pulses are

not received, the link detector disables the 10BASE-T twisted pair transmitter, receiver and collision

detection functions.

When the link integrity function is disabled (FORCE_LINK_10 of the 10BTSCR register), a good link is

forced and the 10BASE-T transceiver will operate regardless of the presence of link pulses.

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