MC9S12NE64_06 Datasheet, PDF (374/554 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 12 Ethernet Physical Transceiver (EPHYV2)
PCS
PMA
TX
4B5B
ENCODER
PARALLEL
TO
SERIAL
SCRAMBLER
PMD
MLT3
ENCODER
SLOPE
CONTROL
LINE
DRIVER
MII
CARRIER
PMA
SENSE
DIGITAL ANALOG
LOOPBACK LOOPBACK
(bit 0.14) (bit 18.4)
LINK
MONITOR
SERIAL TO
RX
4B5B
PARALLEL
DECODER ^{AND SYMBOL}
ALIGNMENT
DESCRAMBLER
MLT3
DECODER
EQUALIZER
AND
TIMING
RECOVERY
BASELINE
WANDER
Figure 12-22. 100BASE-TX Block Diagram
12.4.4.1 Sublayers
12.4.4.1.1 PCS Sublayer
The PCS sublayer is the MII interface that provides a uniform interface to the reconciliation sublayer.
The services provided by the PCS include:
• Encoding/decoding of MII data nibbles to/from 5-bit code-groups (4B/5B)
• Carrier sense and collision indications
• Serialization/deserialization of code-groups for transmission/reception on the PMA
• Mapping of transmit, receive, carrier sense, and collision detection between the MII and the
underlying PMA
Serial to Parallel and Symbol Alignment: This block looks for the occurrence of the JK symbol to align
the serial bit stream and convert it to a parallel format.
Carrier Sense: In full-duplex mode, carrier sense is only asserted while the receive channel is active. The
carrier sense examines the received data bit stream looking for the SSD, the JK symbol pair. In the idle
state, IDLE symbols (all logic ones) will be received. If the first 5-bit symbols received after an idle stream
forms the J symbol (11000) it asserts the CRS signal. At this point the second symbol is checked to confirm
the K symbol (10001). If successful, the following aligned data (symbols) are presented to the 4B/5B
decoder. If the JK pair is not confirmed, the false carrier detect is asserted and the idle state is re-entered.
Carrier sense is de-asserted when the ESD (end-of-stream) delimiter, the TR symbol pair, is found, or when
an idle state is detected.
In half-duplex, CRS is also asserted on transmit.
Parallel to Serial: This block takes parallel data and converts it to serial format.
MC9S12NE64 Data Sheet, Rev. 1.1
374
Freescale Semiconductor