Specifications

DP83848Q-Q1
SNLS341C –MARCH 2011–REVISED MARCH 2015 www.ti.com
5.5.1.3.4 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.
5.5.1.3.5 Normal Link Pulse Detection and 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.
5.5.1.3.6 Jabber Function
The jabber function monitors the output of DP83848Q-Q1 and disables the transmitter if it tries 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 de-asserted 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.
5.5.1.3.7 Automatic Link Polarity Detection and Correction
The DP83848Q-Q1'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 DP83848Q-Q1'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.
5.5.1.3.8 Transmit and Receive Filtering
External 10BASE-T filters are not required when using the DP83848Q-Q1, 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.
5.5.1.3.9 Transmitter
The encoder begins operation when the Transmit Enable input (TX_EN) goes high and converts NRZ data
to pre-emphasized Manchester data for the transceiver. For the duration of TX_EN, the serialized
Transmit Data (TXD) is encoded for the transmit-driver pair (PMD Output Pair). TXD must be valid on the
rising edge of Transmit Clock (TX_CLK). Transmission ends when TX_EN deasserts. The last transition is
always positive; it occurs at the center of the bit cell if the last bit is a one, or at the end of the bit cell if the
last bit is a zero.
44 Detailed Description Copyright © 2011–2015, Texas Instruments Incorporated
Submit Documentation Feedback
Product Folder Links: DP83848Q-Q1