Specifications

DP83848C , DP83848I
DP83848VYB, DP83848YB
www.ti.com SNLS266E –MAY 2007–REVISED MARCH 2015
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 DP83848VYB'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 DP83848VYB'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 DP83848VYB'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 DP83848VYB, 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.
Copyright © 2007–2015, Texas Instruments Incorporated Detailed Description 47
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