DM9161CI DAVICOM [Davicom Semiconductor, Inc.], DM9161CI Datasheet - Page 20

• Manufacturer Part Number: DM9161CI
• Description: Industrial-Temperature 10/100 Mbps Fast Ethernet Physical Layer Single Chip Transceiver
• Manufacturer: DAVICOM [Davicom Semiconductor, Inc.]

The Clock Recovery Module accepts NRZI data from the
MLT-3 to NRZI decoder. The Clock Recovery Module locks
onto the data stream and extracts the 125MHz reference
clock. The extracted and synchronized clock and data are
presented to the NRZI to NRZ Decoder.
7.2.2.5 NRZI to NRZ
The transmit data stream is required to be NRZI encoded in
for compatibility with the TP-PMD standard for 100Base-TX
transmission over Category-5 unshielded twisted pair cable.
This conversion process must be reversed on the receive
end. The NRZI to NRZ decoder receives the NRZI
data stream from the Clock Recovery Module and
converts it to a NRZ data stream to be presented to
the Serial to Parallel conversion block.
7.2.2.6 Serial to Parallel
The Serial to Parallel Converter receives a serial data
stream from the NRZI to NRZ converter, and converts
the data stream to parallel data to be presented to the
descrambler.
7.2.2.7 Descrambler
Because the scrambling process requires to control the
radiated emissions of transmit data streams, the receiver
must descramble the receive data streams. The
descrambler receives scrambled parallel data streams from
the Serial to Parallel converter, descrambles the data
streams, and presents the data streams to the Code Group
alignment block.
7.2.2.8 Code Group Alignment
The Code Group Alignment block receives un-aligned
5B data from the descrambler and converts it into 5B
code group data. Code Group Alignment occurs after
the J/K is detected and subsequent data is aligned on
a fixed boundary.
7.2.2.9 4B5B Decoder
The 4B5B Decoder functions as a look-up table that
translates incoming 5B code groups into 4B (Nibble) data.
When receiving a frame, the first 2 5-bit code groups
received are the start-of-frame delimiter (J/K symbols). The
J/K symbol pair is stripped and two nibbles of preamble
pattern are substituted. The last two code groups are the
22
10/100 Mbps Fast Ethernet Physical Layer Single Chip Transceiver
end-of-frame delimiter (T/R symbols).
The T/R symbol pair is also stripped from the nibble
presented to the Reconciliation layer.
7.2.3 10Base-T Operation
The 10Base-T transceiver is IEEE 802.3u compliant. When
the DM9161CI is operating in 10Base-T mode, the coding
scheme is Manchester. Data processed for transmit is
presented to the MII interface in nibble format, converted to
a serial bit stream, then Manchester encoded. When
receiving, the Manchester encoded bit stream is decoded
and converted into nibble format for presentation to the MII
interface.
7.2.4 Collision Detection
For half-duplex operation, a collision is detected when the
transmit and receive channels are active simultaneously.
When a collision has been detected, it will be reported by the
COL signal on the MII interface. Collision detection is
disabled in Full Duplex operation.
7.2.5 Carrier Sense
Carrier Sense (CRS) is asserted in half-duplex operation
during transmission or reception of data. During full-duplex
mode, CRS is asserted only during receive operations.
7.2.6 Auto-Negotiation
The objective of Auto-negotiation is to provide a means to
exchange information between segment linked devices and
to automatically configure both devices to take maximum
advantage of their abilities. It is important to note that Auto-
negotiation does not test the link segment characteristics.
The Auto-Negotiation function provides a means for a
device to advertise supported modes of operation to a
remote link partner, acknowledge the receipt and
understanding of common modes of operation, and to reject
un-shared modes of operation. This allows devices on both
ends of a segment to establish a link at the best common
mode of operation. If more than one common mode exists
between the two devices, a mechanism is provided to allow
the devices to resolve to a single mode of operation using a
predetermined
priority
Version: DM9161CI-DS-F01
resolution
DM9161CI
February 22, 2012
function.
Final