LAN9730 Datasheet, PDF (80/222 Pages) SMSC Corporation – High-Speed Inter-Chip (HSIC) USB 2.0

LAN9730/LAN9730i
4.6.2.7 Receiver Errors
During a frame, unexpected code-groups are considered receive errors. Expected code groups are the DATA set (0
through F), and the /T/R/ (ESD) symbol pair. When a receive error occurs, the internal MII’s RX_ER signal is asserted
and arbitrary data is driven onto the internal receive data bus (RXD) to the MAC. Should an error be detected during the
time that the /J/K/ delimiter is being decoded (bad SSD error), RX_ER is asserted and the value 1110b is driven onto
the internal receive data bus (RXD) to the MAC. Note that the internal MII’s data valid signal (RX_DV) is not yet asserted
when the bad SSD occurs.
4.6.3 10BASE-T TRANSMIT
Data to be transmitted comes from the MAC layer controller. The 10Base-T transmitter receives 4-bit nibbles from the
MII at a rate of 2.5 MHz and converts them to a 10 Mbps serial data stream. The data stream is then Manchester
encoded and sent to the analog transmitter, which drives a signal onto the twisted pair via the external magnetics.
The 10M transmitter uses the following blocks:
• MII (digital)
• TX 10M (digital)
• 10M Transmitter (analog)
• 10M PLL (analog)
4.6.3.1 10M Transmit Data Across the Internal MII Bus
The MAC controller drives the transmit data onto the internal TXD BUS. When the controller has driven TX_EN high to
indicate valid data, the data is latched by the MII block on the rising edge of TX_CLK. The data is in the form of 4-bit
wide 2.5 MHz data.
4.6.3.2 Manchester Encoding
The 4-bit wide data is sent to the TX10M block. The nibbles are converted to a 10 Mbps serial NRZI data stream. The
10M PLL locks onto the external clock or internal oscillator and produces a 20 MHz clock. This is used to Manchester
encode the NRZ data stream. When no data is being transmitted (TX_EN is low), the TX10M block outputs Normal Link
Pulses (NLPs) to maintain communications with the remote link partner.
4.6.3.3 10M Transmit Drivers
The Manchester encoded data is sent to the analog transmitter where it is shaped and filtered before being driven out
as a differential signal across the TXP and TXN outputs.
4.6.4 10BASE-T RECEIVE
The 10BASE-T receiver gets the Manchester encoded analog signal from the cable via the magnetics. It recovers the
receive clock from the signal and uses this clock to recover the NRZI data stream. This 10M serial data is converted to
4-bit data nibbles which are passed to the controller across the MII at a rate of 2.5 MHz.
This 10M receiver uses the following blocks:
• Filter and SQUELCH (analog)
• 10M PLL (analog)
• RX 10M (digital)
• MII (digital)
DS00001946A-page 80
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