DP83848JSQSLASHNOPB datasheet(46/84 Pages) TI1

46 / 84 page

DP83848H, DP83848J, DP83848K, DP83848M, DP83848T

SNLS250E – MAY 2008 – REVISED APRIL 2015

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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 in the 10BTSCR register.

6.5.1.3.4 Carrier Sense

Carrier Sense (CRS) may be asserted due to receive activity once valid data is detected through 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.

6.5.1.3.5 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.

6.5.1.3.6 Jabber Function

The jabber function monitors the DP83848x's output and disables the transmitter if it attempts to transmit a

packet of longer than legal size. A jabber timer monitors the transmitter and disables the transmission if

the transmitter is active for approximately 85 ms.

Once disabled by the Jabber function, the transmitter stays disabled for the entire time that the ENDEC

module's internal transmit enable is asserted. This signal has to be deasserted for approximately 500 ms

(the “unjab” time) before the Jabber function re-enables the transmit outputs.

The Jabber function is only relevant in 10BASE-T mode.

6.5.1.3.7 Automatic Link Polarity Detection and Correction

The DP83848x's 10BASE-T transceiver module incorporates an automatic link polarity detection circuit.

When three consecutive inverted link pulses are received, bad polarity is reported.

A polarity reversal can be caused by a wiring error at either end of the cable, usually at the Main

Distribution Frame (MDF) or patch panel in the wiring closet.

The bad polarity condition is latched in the 10BTSCR register. The DP83848x's 10BASE-T transceiver

module corrects for this error internally and will continue to decode received data correctly. This eliminates

the need to correct the wiring error immediately.

6.5.1.3.8 Transmit and Receive Filtering

External 10BASE-T filters are not required when using the DP83848x, as the required signal conditioning

is integrated into the device.

Only isolation transformers and impedance matching resistors are required for the 10BASE-T transmit and

receive interface. The internal transmit filtering ensures that all the harmonics in the transmit signal are

attenuated by at least 30 dB.

Detailed Description

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Product Folder Links: DP83848H DP83848J DP83848K DP83848M DP83848T

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