W3100A Datasheet, PDF (49/63 Pages) List of Unclassifed Manufacturers – i2Chip W3100A

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5.2.2 nibble MII
This mode is the I/F for 10/100Mbps Physical Layer Devices, and is composed of 4-bit TXD[0:3] and
RXD[0:3]. TX_CLK and RX_CLK use a 2.5MHz cycle at 10Mbps and 25MHz at 100Mbps.
When linking the W3100A with the Physical Layer Device in this mode, RXD[0:3] and TXD[0:3] of the
Physical Layer Device must be connected to RXD[0:3] and TXD[0:3] of the W3100A.
The W3100A supports both the serial mode and the nibble mode.
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5.2.3 MII Frame Format
TXEN = 0
TXEN = 1
Start
IDLE
PREAMBLE of Frame
DATA Nibbles
Delimiter
PREAMBLE
SFD
DATA1 DATA2
DATA N-1
62B
2B
DATA N
TXEN = 0
IDLE
PREAMBLE
SFD
DATA
IDLE
1 0 1 0 … … 62 bits long
11
Between 64 – 1518 data bytes
TXEN = 0
5.3.4 Nibble MII Order
MAC’s SERIAL BIT STREAM
LSB
D0
D1
D2 D3 D4 D5
D6
D7
FIRST NIBBLE
TXD0/RXD0
MSB
SECOND
NIBBLE
TXD1/RXD1
TXD2/RXD2
TXD3/RXD3
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