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Ethernet Physical Transceiver (EPHY)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
19-27
Figure 19-21. 10BASE-T Block Diagram
Parallel to Serial:
Converts the 4-bit wide nibbles from the MII to serial format before the information is
processed by subsequent blocks.
Manchester Encoder:
Allows encoding of the clock and data in one bit stream. A logical one is encoded
as a zero when the clock is high and a one when the clock is low. A logical zero is encoded as a one when
the clock is high and a zero when the clock is low.
Digital Filter:
Performs pre-emphasis and low pass filtering of the input Manchester data.
DAC:
Converts the digital data to an analog format before transmission on the media.
Carrier Sense:
In half-duplex operation, carrier is asserted when the transmit or receive medium is active.
In full-duplex operation, carrier asserted only on reception of data. During receive, carrier sense is asserted
during reception of a valid preamble, and de-asserted after reception of an EOF.
Loopback:
Enabled when bit 0.14 is asserted. This loopback mode allows for the Manchester encoded and
filtered data to be looped back to the squelch block in the receive path. All the 10BASE-T digital functions
are exercised during this mode. The transmit and receive channels are disconnected from the media.
MII loopback (18.13) must be disabled to allow for correct operation of the digital loopback (0.14).
Link Generator:
Generates a 100 ns duration pulse at the end of every 12 ms period of the transmission
path being idle (TXEN de-asserted). This pulse is used to keep the 10BASE-T link operational in the
absence of data transmission.
Link Integrity Test:
Used to determine whether the 10BASE-T link is operational. If neither data nor a
link pulse is received for 64 ms, then the link is considered down. While the link is down, the transmit,
Serial
Parallel
Digital
to
Parallel
to
Serial
MII
MII
TX
RX
Manchester
Encoder
Filter
Carrier
Sense
Jabber
Manchester
Decoder
and
Timing
Recovery
Polarity
Check
Squelch
Digital
Loopback
(bit 0.14)
PHY_TXN
PHY_TXP
PHY_RXN
PHY_RXP
Line Transmitter/
Line Receiver
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60